Ordinal multiplication












0














I understand why $(omega+1)cdot2 = omegacdot2+1$ and why $(omega+1)cdotomega = omega^2$



What I am struggling with is something along the lines of:



$(omegacdot3+4)cdot3$ which I think is = $omegacdot9+4$



And:



$(omegacdot3+4)(omegacdot3)$ which I think is = $omega^2cdot9$



Am I correct?










share|cite|improve this question
























  • Could you explain how to evaluate them?
    – Hanul Jeon
    Nov 25 at 5:08










  • (w.3 + 4).3 = (w.3 + 4) + (w.3 + 4) + (w.3 + 4) = w.3 + (4 + w.3) + (4 + w.3) + 4 = w.3 + w.3 + w.3 + 4 = w.9 + 4 ??
    – Fraiku
    Nov 25 at 9:22












  • Your first evaluation is correct; however the second one is not valid.
    – Hanul Jeon
    Nov 25 at 9:27










  • Thank you. I was following this explanation for (w + 1).w^2 and trying to extrapolate, but I'm not sure where I've gone wrong. Can you clarify?
    – Fraiku
    Nov 25 at 9:41


















0














I understand why $(omega+1)cdot2 = omegacdot2+1$ and why $(omega+1)cdotomega = omega^2$



What I am struggling with is something along the lines of:



$(omegacdot3+4)cdot3$ which I think is = $omegacdot9+4$



And:



$(omegacdot3+4)(omegacdot3)$ which I think is = $omega^2cdot9$



Am I correct?










share|cite|improve this question
























  • Could you explain how to evaluate them?
    – Hanul Jeon
    Nov 25 at 5:08










  • (w.3 + 4).3 = (w.3 + 4) + (w.3 + 4) + (w.3 + 4) = w.3 + (4 + w.3) + (4 + w.3) + 4 = w.3 + w.3 + w.3 + 4 = w.9 + 4 ??
    – Fraiku
    Nov 25 at 9:22












  • Your first evaluation is correct; however the second one is not valid.
    – Hanul Jeon
    Nov 25 at 9:27










  • Thank you. I was following this explanation for (w + 1).w^2 and trying to extrapolate, but I'm not sure where I've gone wrong. Can you clarify?
    – Fraiku
    Nov 25 at 9:41
















0












0








0







I understand why $(omega+1)cdot2 = omegacdot2+1$ and why $(omega+1)cdotomega = omega^2$



What I am struggling with is something along the lines of:



$(omegacdot3+4)cdot3$ which I think is = $omegacdot9+4$



And:



$(omegacdot3+4)(omegacdot3)$ which I think is = $omega^2cdot9$



Am I correct?










share|cite|improve this question















I understand why $(omega+1)cdot2 = omegacdot2+1$ and why $(omega+1)cdotomega = omega^2$



What I am struggling with is something along the lines of:



$(omegacdot3+4)cdot3$ which I think is = $omegacdot9+4$



And:



$(omegacdot3+4)(omegacdot3)$ which I think is = $omega^2cdot9$



Am I correct?







elementary-set-theory ordinals






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Nov 25 at 10:15









Holo

5,5062930




5,5062930










asked Nov 24 at 21:41









Fraiku

102




102












  • Could you explain how to evaluate them?
    – Hanul Jeon
    Nov 25 at 5:08










  • (w.3 + 4).3 = (w.3 + 4) + (w.3 + 4) + (w.3 + 4) = w.3 + (4 + w.3) + (4 + w.3) + 4 = w.3 + w.3 + w.3 + 4 = w.9 + 4 ??
    – Fraiku
    Nov 25 at 9:22












  • Your first evaluation is correct; however the second one is not valid.
    – Hanul Jeon
    Nov 25 at 9:27










  • Thank you. I was following this explanation for (w + 1).w^2 and trying to extrapolate, but I'm not sure where I've gone wrong. Can you clarify?
    – Fraiku
    Nov 25 at 9:41




















  • Could you explain how to evaluate them?
    – Hanul Jeon
    Nov 25 at 5:08










  • (w.3 + 4).3 = (w.3 + 4) + (w.3 + 4) + (w.3 + 4) = w.3 + (4 + w.3) + (4 + w.3) + 4 = w.3 + w.3 + w.3 + 4 = w.9 + 4 ??
    – Fraiku
    Nov 25 at 9:22












  • Your first evaluation is correct; however the second one is not valid.
    – Hanul Jeon
    Nov 25 at 9:27










  • Thank you. I was following this explanation for (w + 1).w^2 and trying to extrapolate, but I'm not sure where I've gone wrong. Can you clarify?
    – Fraiku
    Nov 25 at 9:41


















Could you explain how to evaluate them?
– Hanul Jeon
Nov 25 at 5:08




Could you explain how to evaluate them?
– Hanul Jeon
Nov 25 at 5:08












(w.3 + 4).3 = (w.3 + 4) + (w.3 + 4) + (w.3 + 4) = w.3 + (4 + w.3) + (4 + w.3) + 4 = w.3 + w.3 + w.3 + 4 = w.9 + 4 ??
– Fraiku
Nov 25 at 9:22






(w.3 + 4).3 = (w.3 + 4) + (w.3 + 4) + (w.3 + 4) = w.3 + (4 + w.3) + (4 + w.3) + 4 = w.3 + w.3 + w.3 + 4 = w.9 + 4 ??
– Fraiku
Nov 25 at 9:22














Your first evaluation is correct; however the second one is not valid.
– Hanul Jeon
Nov 25 at 9:27




Your first evaluation is correct; however the second one is not valid.
– Hanul Jeon
Nov 25 at 9:27












Thank you. I was following this explanation for (w + 1).w^2 and trying to extrapolate, but I'm not sure where I've gone wrong. Can you clarify?
– Fraiku
Nov 25 at 9:41






Thank you. I was following this explanation for (w + 1).w^2 and trying to extrapolate, but I'm not sure where I've gone wrong. Can you clarify?
– Fraiku
Nov 25 at 9:41












1 Answer
1






active

oldest

votes


















0














You have evaluated $(omegacdot 3+4)cdot 3$ correctly. However, $(omegacdot 3+4)cdot(omegacdot 3)$ is not correctly evaluated. I do not know which step of your evaluation is incorrect, but I guess you think adding $(omegacdot 3)$ $(omegacdot 3)$ times is $omega^2cdot 9$.



This is not true, however, as
$$(omegacdot 3)cdot (omegacdot 3) = omegacdot (3cdotomega)cdot 3 = omega^2cdot 3.$$
The core part of the evaluation is $3cdotomega=omega$ that can be proven in the way of proving $3+omega =omega$ (and the linked question in your comment.)



We would think evaluating $(omegacdot 3+4)cdot(omegacdot 3)$ is not too different from that of $(omegacdot 3)cdot (omegacdot 3)$. The problem is, we have extra $+4$ and we cannot apply the distribution law in the case.
However, the addition in the middle of the expression would disappear when adding $(omegacdot 3+4)$ many times, so we can guess the answer is $omega^2cdot 3$.



You can make our discussion concretely by following the steps of the proof you have linked; that is, use the transfinite induction for $betale omegacdot 3$ to prove
$$(omegacdot 3+4)cdotbeta = begin{cases}
omegacdot (3cdotbeta) &text{if $beta$ is a limit ordinal,} \ omegacdot (3cdotbeta) + 4 & text{if $beta$ is a successor ordinal.}end{cases}$$






share|cite|improve this answer





















  • Ahh I see, thank you very much. So would I right in saying then that something like (w⋅2+2)⋅(w⋅3) would = (w^2).3 ?
    – Fraiku
    Nov 25 at 10:25










  • @Fraiku Yes. $!$
    – Hanul Jeon
    Nov 25 at 10:26










  • Sorry, you are being so helpful I hope you don't mind if I ask you another question. Given the lack of distributive law on the right, I am struggling to know where to start to tackle more complex multiplications such as: ((w^2).2)+(w.3+1))5 or ((w^2).2)+(w.3+1))(w.5)
    – Fraiku
    Nov 25 at 10:32












  • @Fraiku The easiest strategy is evaluate $alphacdotbeta$ for small $beta$ and guess the pattern.
    – Hanul Jeon
    Nov 25 at 10:34










  • So ((w^2).2)+(w.3+1))2 = ((w^2).2)+(w.3+1)+((w^2).2)+(w.3+1) = ((w^2).2)+((w^2).2)+(w.3+1) = ((w^2).4)+w.3+1?
    – Fraiku
    Nov 25 at 10:40











Your Answer





StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "69"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});














draft saved

draft discarded


















StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3012120%2fordinal-multiplication%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown

























1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









0














You have evaluated $(omegacdot 3+4)cdot 3$ correctly. However, $(omegacdot 3+4)cdot(omegacdot 3)$ is not correctly evaluated. I do not know which step of your evaluation is incorrect, but I guess you think adding $(omegacdot 3)$ $(omegacdot 3)$ times is $omega^2cdot 9$.



This is not true, however, as
$$(omegacdot 3)cdot (omegacdot 3) = omegacdot (3cdotomega)cdot 3 = omega^2cdot 3.$$
The core part of the evaluation is $3cdotomega=omega$ that can be proven in the way of proving $3+omega =omega$ (and the linked question in your comment.)



We would think evaluating $(omegacdot 3+4)cdot(omegacdot 3)$ is not too different from that of $(omegacdot 3)cdot (omegacdot 3)$. The problem is, we have extra $+4$ and we cannot apply the distribution law in the case.
However, the addition in the middle of the expression would disappear when adding $(omegacdot 3+4)$ many times, so we can guess the answer is $omega^2cdot 3$.



You can make our discussion concretely by following the steps of the proof you have linked; that is, use the transfinite induction for $betale omegacdot 3$ to prove
$$(omegacdot 3+4)cdotbeta = begin{cases}
omegacdot (3cdotbeta) &text{if $beta$ is a limit ordinal,} \ omegacdot (3cdotbeta) + 4 & text{if $beta$ is a successor ordinal.}end{cases}$$






share|cite|improve this answer





















  • Ahh I see, thank you very much. So would I right in saying then that something like (w⋅2+2)⋅(w⋅3) would = (w^2).3 ?
    – Fraiku
    Nov 25 at 10:25










  • @Fraiku Yes. $!$
    – Hanul Jeon
    Nov 25 at 10:26










  • Sorry, you are being so helpful I hope you don't mind if I ask you another question. Given the lack of distributive law on the right, I am struggling to know where to start to tackle more complex multiplications such as: ((w^2).2)+(w.3+1))5 or ((w^2).2)+(w.3+1))(w.5)
    – Fraiku
    Nov 25 at 10:32












  • @Fraiku The easiest strategy is evaluate $alphacdotbeta$ for small $beta$ and guess the pattern.
    – Hanul Jeon
    Nov 25 at 10:34










  • So ((w^2).2)+(w.3+1))2 = ((w^2).2)+(w.3+1)+((w^2).2)+(w.3+1) = ((w^2).2)+((w^2).2)+(w.3+1) = ((w^2).4)+w.3+1?
    – Fraiku
    Nov 25 at 10:40
















0














You have evaluated $(omegacdot 3+4)cdot 3$ correctly. However, $(omegacdot 3+4)cdot(omegacdot 3)$ is not correctly evaluated. I do not know which step of your evaluation is incorrect, but I guess you think adding $(omegacdot 3)$ $(omegacdot 3)$ times is $omega^2cdot 9$.



This is not true, however, as
$$(omegacdot 3)cdot (omegacdot 3) = omegacdot (3cdotomega)cdot 3 = omega^2cdot 3.$$
The core part of the evaluation is $3cdotomega=omega$ that can be proven in the way of proving $3+omega =omega$ (and the linked question in your comment.)



We would think evaluating $(omegacdot 3+4)cdot(omegacdot 3)$ is not too different from that of $(omegacdot 3)cdot (omegacdot 3)$. The problem is, we have extra $+4$ and we cannot apply the distribution law in the case.
However, the addition in the middle of the expression would disappear when adding $(omegacdot 3+4)$ many times, so we can guess the answer is $omega^2cdot 3$.



You can make our discussion concretely by following the steps of the proof you have linked; that is, use the transfinite induction for $betale omegacdot 3$ to prove
$$(omegacdot 3+4)cdotbeta = begin{cases}
omegacdot (3cdotbeta) &text{if $beta$ is a limit ordinal,} \ omegacdot (3cdotbeta) + 4 & text{if $beta$ is a successor ordinal.}end{cases}$$






share|cite|improve this answer





















  • Ahh I see, thank you very much. So would I right in saying then that something like (w⋅2+2)⋅(w⋅3) would = (w^2).3 ?
    – Fraiku
    Nov 25 at 10:25










  • @Fraiku Yes. $!$
    – Hanul Jeon
    Nov 25 at 10:26










  • Sorry, you are being so helpful I hope you don't mind if I ask you another question. Given the lack of distributive law on the right, I am struggling to know where to start to tackle more complex multiplications such as: ((w^2).2)+(w.3+1))5 or ((w^2).2)+(w.3+1))(w.5)
    – Fraiku
    Nov 25 at 10:32












  • @Fraiku The easiest strategy is evaluate $alphacdotbeta$ for small $beta$ and guess the pattern.
    – Hanul Jeon
    Nov 25 at 10:34










  • So ((w^2).2)+(w.3+1))2 = ((w^2).2)+(w.3+1)+((w^2).2)+(w.3+1) = ((w^2).2)+((w^2).2)+(w.3+1) = ((w^2).4)+w.3+1?
    – Fraiku
    Nov 25 at 10:40














0












0








0






You have evaluated $(omegacdot 3+4)cdot 3$ correctly. However, $(omegacdot 3+4)cdot(omegacdot 3)$ is not correctly evaluated. I do not know which step of your evaluation is incorrect, but I guess you think adding $(omegacdot 3)$ $(omegacdot 3)$ times is $omega^2cdot 9$.



This is not true, however, as
$$(omegacdot 3)cdot (omegacdot 3) = omegacdot (3cdotomega)cdot 3 = omega^2cdot 3.$$
The core part of the evaluation is $3cdotomega=omega$ that can be proven in the way of proving $3+omega =omega$ (and the linked question in your comment.)



We would think evaluating $(omegacdot 3+4)cdot(omegacdot 3)$ is not too different from that of $(omegacdot 3)cdot (omegacdot 3)$. The problem is, we have extra $+4$ and we cannot apply the distribution law in the case.
However, the addition in the middle of the expression would disappear when adding $(omegacdot 3+4)$ many times, so we can guess the answer is $omega^2cdot 3$.



You can make our discussion concretely by following the steps of the proof you have linked; that is, use the transfinite induction for $betale omegacdot 3$ to prove
$$(omegacdot 3+4)cdotbeta = begin{cases}
omegacdot (3cdotbeta) &text{if $beta$ is a limit ordinal,} \ omegacdot (3cdotbeta) + 4 & text{if $beta$ is a successor ordinal.}end{cases}$$






share|cite|improve this answer












You have evaluated $(omegacdot 3+4)cdot 3$ correctly. However, $(omegacdot 3+4)cdot(omegacdot 3)$ is not correctly evaluated. I do not know which step of your evaluation is incorrect, but I guess you think adding $(omegacdot 3)$ $(omegacdot 3)$ times is $omega^2cdot 9$.



This is not true, however, as
$$(omegacdot 3)cdot (omegacdot 3) = omegacdot (3cdotomega)cdot 3 = omega^2cdot 3.$$
The core part of the evaluation is $3cdotomega=omega$ that can be proven in the way of proving $3+omega =omega$ (and the linked question in your comment.)



We would think evaluating $(omegacdot 3+4)cdot(omegacdot 3)$ is not too different from that of $(omegacdot 3)cdot (omegacdot 3)$. The problem is, we have extra $+4$ and we cannot apply the distribution law in the case.
However, the addition in the middle of the expression would disappear when adding $(omegacdot 3+4)$ many times, so we can guess the answer is $omega^2cdot 3$.



You can make our discussion concretely by following the steps of the proof you have linked; that is, use the transfinite induction for $betale omegacdot 3$ to prove
$$(omegacdot 3+4)cdotbeta = begin{cases}
omegacdot (3cdotbeta) &text{if $beta$ is a limit ordinal,} \ omegacdot (3cdotbeta) + 4 & text{if $beta$ is a successor ordinal.}end{cases}$$







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Nov 25 at 9:51









Hanul Jeon

17.5k42780




17.5k42780












  • Ahh I see, thank you very much. So would I right in saying then that something like (w⋅2+2)⋅(w⋅3) would = (w^2).3 ?
    – Fraiku
    Nov 25 at 10:25










  • @Fraiku Yes. $!$
    – Hanul Jeon
    Nov 25 at 10:26










  • Sorry, you are being so helpful I hope you don't mind if I ask you another question. Given the lack of distributive law on the right, I am struggling to know where to start to tackle more complex multiplications such as: ((w^2).2)+(w.3+1))5 or ((w^2).2)+(w.3+1))(w.5)
    – Fraiku
    Nov 25 at 10:32












  • @Fraiku The easiest strategy is evaluate $alphacdotbeta$ for small $beta$ and guess the pattern.
    – Hanul Jeon
    Nov 25 at 10:34










  • So ((w^2).2)+(w.3+1))2 = ((w^2).2)+(w.3+1)+((w^2).2)+(w.3+1) = ((w^2).2)+((w^2).2)+(w.3+1) = ((w^2).4)+w.3+1?
    – Fraiku
    Nov 25 at 10:40


















  • Ahh I see, thank you very much. So would I right in saying then that something like (w⋅2+2)⋅(w⋅3) would = (w^2).3 ?
    – Fraiku
    Nov 25 at 10:25










  • @Fraiku Yes. $!$
    – Hanul Jeon
    Nov 25 at 10:26










  • Sorry, you are being so helpful I hope you don't mind if I ask you another question. Given the lack of distributive law on the right, I am struggling to know where to start to tackle more complex multiplications such as: ((w^2).2)+(w.3+1))5 or ((w^2).2)+(w.3+1))(w.5)
    – Fraiku
    Nov 25 at 10:32












  • @Fraiku The easiest strategy is evaluate $alphacdotbeta$ for small $beta$ and guess the pattern.
    – Hanul Jeon
    Nov 25 at 10:34










  • So ((w^2).2)+(w.3+1))2 = ((w^2).2)+(w.3+1)+((w^2).2)+(w.3+1) = ((w^2).2)+((w^2).2)+(w.3+1) = ((w^2).4)+w.3+1?
    – Fraiku
    Nov 25 at 10:40
















Ahh I see, thank you very much. So would I right in saying then that something like (w⋅2+2)⋅(w⋅3) would = (w^2).3 ?
– Fraiku
Nov 25 at 10:25




Ahh I see, thank you very much. So would I right in saying then that something like (w⋅2+2)⋅(w⋅3) would = (w^2).3 ?
– Fraiku
Nov 25 at 10:25












@Fraiku Yes. $!$
– Hanul Jeon
Nov 25 at 10:26




@Fraiku Yes. $!$
– Hanul Jeon
Nov 25 at 10:26












Sorry, you are being so helpful I hope you don't mind if I ask you another question. Given the lack of distributive law on the right, I am struggling to know where to start to tackle more complex multiplications such as: ((w^2).2)+(w.3+1))5 or ((w^2).2)+(w.3+1))(w.5)
– Fraiku
Nov 25 at 10:32






Sorry, you are being so helpful I hope you don't mind if I ask you another question. Given the lack of distributive law on the right, I am struggling to know where to start to tackle more complex multiplications such as: ((w^2).2)+(w.3+1))5 or ((w^2).2)+(w.3+1))(w.5)
– Fraiku
Nov 25 at 10:32














@Fraiku The easiest strategy is evaluate $alphacdotbeta$ for small $beta$ and guess the pattern.
– Hanul Jeon
Nov 25 at 10:34




@Fraiku The easiest strategy is evaluate $alphacdotbeta$ for small $beta$ and guess the pattern.
– Hanul Jeon
Nov 25 at 10:34












So ((w^2).2)+(w.3+1))2 = ((w^2).2)+(w.3+1)+((w^2).2)+(w.3+1) = ((w^2).2)+((w^2).2)+(w.3+1) = ((w^2).4)+w.3+1?
– Fraiku
Nov 25 at 10:40




So ((w^2).2)+(w.3+1))2 = ((w^2).2)+(w.3+1)+((w^2).2)+(w.3+1) = ((w^2).2)+((w^2).2)+(w.3+1) = ((w^2).4)+w.3+1?
– Fraiku
Nov 25 at 10:40


















draft saved

draft discarded




















































Thanks for contributing an answer to Mathematics Stack Exchange!


  • Please be sure to answer the question. Provide details and share your research!

But avoid



  • Asking for help, clarification, or responding to other answers.

  • Making statements based on opinion; back them up with references or personal experience.


Use MathJax to format equations. MathJax reference.


To learn more, see our tips on writing great answers.





Some of your past answers have not been well-received, and you're in danger of being blocked from answering.


Please pay close attention to the following guidance:


  • Please be sure to answer the question. Provide details and share your research!

But avoid



  • Asking for help, clarification, or responding to other answers.

  • Making statements based on opinion; back them up with references or personal experience.


To learn more, see our tips on writing great answers.




draft saved


draft discarded














StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3012120%2fordinal-multiplication%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown





















































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown

































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown







Popular posts from this blog

Plaza Victoria

In PowerPoint, is there a keyboard shortcut for bulleted / numbered list?

How to put 3 figures in Latex with 2 figures side by side and 1 below these side by side images but in...