[问答题]
Let the Maclaurin seri
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$\cot x=\frac{a_{1}}{x}+a_{2} x+a_{3} x^{3}+\cdots$
where $a_{1}, a_{2}$ and $ a_{3}$ are non zero constants.
1. Find the series for $\csc ^{2}$ x , in terms of $a_{1}, a_{2}$ and $a_{3}$ , up to and including the $x^{2}$ term
a. by differentiating the above series for $\cot x$ ;
b. by using the relationship $\csc ^{2} x=1+\cot ^{2} x$ .
2. Hence, by comparing your two series, determine the values of $a_{1}, a_{2}$ and $ a_{3}$ .
