Maclaurin's series for $tan(x+x^2)$












1












$begingroup$


I would like to find the Maclaurin's series for $tan(x+x^2)$ stopped at $x_0^3$.



I tried with:
$$tan(x+x^2)=1+frac{1+2x_0}{cos^2(x_0+x_0^2)}x+....,$$ but it seems like the derivation gets more complicated. I was wondering if there was a simpler way to solve the Maclaurin series. I was thinking about putting $t=x+x^2$, but it looks like wrong (why?).



Update:



I know that MacLaurin's expansion for tan(x): $$T(x) = x + frac {1}{3}x^{3} + frac { 2 } { 15 } x ^ { 5 } + frac { 17 } { 315 } x ^ { 7 } + ldots$$ But according to Mathematica, there should be a $x^2$ for the MacLaurin series for $tan(x+x^2)$, which I couldn't understand.










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$endgroup$












  • $begingroup$
    If all you care about is the series and not its derivation, why not use Mathematica? I doubt there is any special trick for this.
    $endgroup$
    – Hamed
    Jan 21 at 14:26












  • $begingroup$
    Could you show me an example? Do you mean substituting $x_0$ with 0 and solving the derivatives?
    $endgroup$
    – Kevin
    Jan 21 at 14:26










  • $begingroup$
    @Hamed Because it is part of a question of my past exams, and we are not allowed to use Mathematica.
    $endgroup$
    – Kevin
    Jan 21 at 14:28






  • 2




    $begingroup$
    Setting $t=x+x^2$ in the series for $tan{t}$ will work fine. Why wouldn't it?
    $endgroup$
    – saulspatz
    Jan 21 at 14:29










  • $begingroup$
    Apparently, the expansion is around an arbitrary point $x_0$ not zero.
    $endgroup$
    – Hamed
    Jan 21 at 14:33
















1












$begingroup$


I would like to find the Maclaurin's series for $tan(x+x^2)$ stopped at $x_0^3$.



I tried with:
$$tan(x+x^2)=1+frac{1+2x_0}{cos^2(x_0+x_0^2)}x+....,$$ but it seems like the derivation gets more complicated. I was wondering if there was a simpler way to solve the Maclaurin series. I was thinking about putting $t=x+x^2$, but it looks like wrong (why?).



Update:



I know that MacLaurin's expansion for tan(x): $$T(x) = x + frac {1}{3}x^{3} + frac { 2 } { 15 } x ^ { 5 } + frac { 17 } { 315 } x ^ { 7 } + ldots$$ But according to Mathematica, there should be a $x^2$ for the MacLaurin series for $tan(x+x^2)$, which I couldn't understand.










share|cite|improve this question











$endgroup$












  • $begingroup$
    If all you care about is the series and not its derivation, why not use Mathematica? I doubt there is any special trick for this.
    $endgroup$
    – Hamed
    Jan 21 at 14:26












  • $begingroup$
    Could you show me an example? Do you mean substituting $x_0$ with 0 and solving the derivatives?
    $endgroup$
    – Kevin
    Jan 21 at 14:26










  • $begingroup$
    @Hamed Because it is part of a question of my past exams, and we are not allowed to use Mathematica.
    $endgroup$
    – Kevin
    Jan 21 at 14:28






  • 2




    $begingroup$
    Setting $t=x+x^2$ in the series for $tan{t}$ will work fine. Why wouldn't it?
    $endgroup$
    – saulspatz
    Jan 21 at 14:29










  • $begingroup$
    Apparently, the expansion is around an arbitrary point $x_0$ not zero.
    $endgroup$
    – Hamed
    Jan 21 at 14:33














1












1








1





$begingroup$


I would like to find the Maclaurin's series for $tan(x+x^2)$ stopped at $x_0^3$.



I tried with:
$$tan(x+x^2)=1+frac{1+2x_0}{cos^2(x_0+x_0^2)}x+....,$$ but it seems like the derivation gets more complicated. I was wondering if there was a simpler way to solve the Maclaurin series. I was thinking about putting $t=x+x^2$, but it looks like wrong (why?).



Update:



I know that MacLaurin's expansion for tan(x): $$T(x) = x + frac {1}{3}x^{3} + frac { 2 } { 15 } x ^ { 5 } + frac { 17 } { 315 } x ^ { 7 } + ldots$$ But according to Mathematica, there should be a $x^2$ for the MacLaurin series for $tan(x+x^2)$, which I couldn't understand.










share|cite|improve this question











$endgroup$




I would like to find the Maclaurin's series for $tan(x+x^2)$ stopped at $x_0^3$.



I tried with:
$$tan(x+x^2)=1+frac{1+2x_0}{cos^2(x_0+x_0^2)}x+....,$$ but it seems like the derivation gets more complicated. I was wondering if there was a simpler way to solve the Maclaurin series. I was thinking about putting $t=x+x^2$, but it looks like wrong (why?).



Update:



I know that MacLaurin's expansion for tan(x): $$T(x) = x + frac {1}{3}x^{3} + frac { 2 } { 15 } x ^ { 5 } + frac { 17 } { 315 } x ^ { 7 } + ldots$$ But according to Mathematica, there should be a $x^2$ for the MacLaurin series for $tan(x+x^2)$, which I couldn't understand.







calculus derivatives taylor-expansion






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share|cite|improve this question













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share|cite|improve this question








edited Jan 21 at 14:53







Kevin

















asked Jan 21 at 14:18









KevinKevin

16211




16211












  • $begingroup$
    If all you care about is the series and not its derivation, why not use Mathematica? I doubt there is any special trick for this.
    $endgroup$
    – Hamed
    Jan 21 at 14:26












  • $begingroup$
    Could you show me an example? Do you mean substituting $x_0$ with 0 and solving the derivatives?
    $endgroup$
    – Kevin
    Jan 21 at 14:26










  • $begingroup$
    @Hamed Because it is part of a question of my past exams, and we are not allowed to use Mathematica.
    $endgroup$
    – Kevin
    Jan 21 at 14:28






  • 2




    $begingroup$
    Setting $t=x+x^2$ in the series for $tan{t}$ will work fine. Why wouldn't it?
    $endgroup$
    – saulspatz
    Jan 21 at 14:29










  • $begingroup$
    Apparently, the expansion is around an arbitrary point $x_0$ not zero.
    $endgroup$
    – Hamed
    Jan 21 at 14:33


















  • $begingroup$
    If all you care about is the series and not its derivation, why not use Mathematica? I doubt there is any special trick for this.
    $endgroup$
    – Hamed
    Jan 21 at 14:26












  • $begingroup$
    Could you show me an example? Do you mean substituting $x_0$ with 0 and solving the derivatives?
    $endgroup$
    – Kevin
    Jan 21 at 14:26










  • $begingroup$
    @Hamed Because it is part of a question of my past exams, and we are not allowed to use Mathematica.
    $endgroup$
    – Kevin
    Jan 21 at 14:28






  • 2




    $begingroup$
    Setting $t=x+x^2$ in the series for $tan{t}$ will work fine. Why wouldn't it?
    $endgroup$
    – saulspatz
    Jan 21 at 14:29










  • $begingroup$
    Apparently, the expansion is around an arbitrary point $x_0$ not zero.
    $endgroup$
    – Hamed
    Jan 21 at 14:33
















$begingroup$
If all you care about is the series and not its derivation, why not use Mathematica? I doubt there is any special trick for this.
$endgroup$
– Hamed
Jan 21 at 14:26






$begingroup$
If all you care about is the series and not its derivation, why not use Mathematica? I doubt there is any special trick for this.
$endgroup$
– Hamed
Jan 21 at 14:26














$begingroup$
Could you show me an example? Do you mean substituting $x_0$ with 0 and solving the derivatives?
$endgroup$
– Kevin
Jan 21 at 14:26




$begingroup$
Could you show me an example? Do you mean substituting $x_0$ with 0 and solving the derivatives?
$endgroup$
– Kevin
Jan 21 at 14:26












$begingroup$
@Hamed Because it is part of a question of my past exams, and we are not allowed to use Mathematica.
$endgroup$
– Kevin
Jan 21 at 14:28




$begingroup$
@Hamed Because it is part of a question of my past exams, and we are not allowed to use Mathematica.
$endgroup$
– Kevin
Jan 21 at 14:28




2




2




$begingroup$
Setting $t=x+x^2$ in the series for $tan{t}$ will work fine. Why wouldn't it?
$endgroup$
– saulspatz
Jan 21 at 14:29




$begingroup$
Setting $t=x+x^2$ in the series for $tan{t}$ will work fine. Why wouldn't it?
$endgroup$
– saulspatz
Jan 21 at 14:29












$begingroup$
Apparently, the expansion is around an arbitrary point $x_0$ not zero.
$endgroup$
– Hamed
Jan 21 at 14:33




$begingroup$
Apparently, the expansion is around an arbitrary point $x_0$ not zero.
$endgroup$
– Hamed
Jan 21 at 14:33










1 Answer
1






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oldest

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1












$begingroup$

Just substitute $x+x^2$ for $x$ in your formula of $T(x):$
$$T(x+x^2)=(x+x^2)+frac13(x+x^2)^3+cdots$$



Now you just have to expand and rearrange the terms. Since you only need powers up through $x^3$, there no need to be concerned with the higher-degree terms in $T(x)$






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Now I get it. Apparently, I had a lot of confusion in my mind. Thank you!
    $endgroup$
    – Kevin
    Jan 21 at 15:09











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1 Answer
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1 Answer
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active

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1












$begingroup$

Just substitute $x+x^2$ for $x$ in your formula of $T(x):$
$$T(x+x^2)=(x+x^2)+frac13(x+x^2)^3+cdots$$



Now you just have to expand and rearrange the terms. Since you only need powers up through $x^3$, there no need to be concerned with the higher-degree terms in $T(x)$






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Now I get it. Apparently, I had a lot of confusion in my mind. Thank you!
    $endgroup$
    – Kevin
    Jan 21 at 15:09
















1












$begingroup$

Just substitute $x+x^2$ for $x$ in your formula of $T(x):$
$$T(x+x^2)=(x+x^2)+frac13(x+x^2)^3+cdots$$



Now you just have to expand and rearrange the terms. Since you only need powers up through $x^3$, there no need to be concerned with the higher-degree terms in $T(x)$






share|cite|improve this answer









$endgroup$













  • $begingroup$
    Now I get it. Apparently, I had a lot of confusion in my mind. Thank you!
    $endgroup$
    – Kevin
    Jan 21 at 15:09














1












1








1





$begingroup$

Just substitute $x+x^2$ for $x$ in your formula of $T(x):$
$$T(x+x^2)=(x+x^2)+frac13(x+x^2)^3+cdots$$



Now you just have to expand and rearrange the terms. Since you only need powers up through $x^3$, there no need to be concerned with the higher-degree terms in $T(x)$






share|cite|improve this answer









$endgroup$



Just substitute $x+x^2$ for $x$ in your formula of $T(x):$
$$T(x+x^2)=(x+x^2)+frac13(x+x^2)^3+cdots$$



Now you just have to expand and rearrange the terms. Since you only need powers up through $x^3$, there no need to be concerned with the higher-degree terms in $T(x)$







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Jan 21 at 14:58









saulspatzsaulspatz

16.3k31332




16.3k31332












  • $begingroup$
    Now I get it. Apparently, I had a lot of confusion in my mind. Thank you!
    $endgroup$
    – Kevin
    Jan 21 at 15:09


















  • $begingroup$
    Now I get it. Apparently, I had a lot of confusion in my mind. Thank you!
    $endgroup$
    – Kevin
    Jan 21 at 15:09
















$begingroup$
Now I get it. Apparently, I had a lot of confusion in my mind. Thank you!
$endgroup$
– Kevin
Jan 21 at 15:09




$begingroup$
Now I get it. Apparently, I had a lot of confusion in my mind. Thank you!
$endgroup$
– Kevin
Jan 21 at 15:09


















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