Mary Boas: Mathematical Methods Problem 1.13.8

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Homework Statement



Using the methods of this section:
(a) Find the first few terms of the Maclaurin series for each of the following functions.
(b) Find the general term and write the series in summation form.
(c) Check your results in (a) by computer.
(d) Use a computer to plot the function and several approximating partial sums of the
series.

#8 \frac { 1 }{ \sqrt { 1-{ x }^{ 2 } } }

Homework Equations



(1+x)^{P}=\sum _{ n=0 }^{ \infty }{ \binom {P} {n}} x^n

The Attempt at a Solution



I got: \frac { 1 }{ \sqrt { 1-{ x }^{ 2 } } }=\sum _{ n=0 }^{ \infty }{ \binom {-1/2} {n}} (1-x^{2})^{n}

Solution manual's solution is: \frac { 1 }{ \sqrt { 1-{ x }^{ 2 } } }=\sum _{ n=0 }^{ \infty }{ \binom {-1/2} {n}} (-x^{2})^{n}

What went wrong?

Thanks,
Chris Maness
 
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I see my mistake. I made a bad assumption when I subbed in 1+x^2=t+1. I needed to solve for t before I subbed it back in.

Thanks,
Chris Maness
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...

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