If $f(x)=\frac{\cos x}{\sin ^2 x+\cos ^4 x}$, for $x \in R$, then $f(2002)$ is equal to

If $f(x)=\frac{\cos x}{\sin ^2 x+\cos ^4 x}$, for $x \in R$, then $f(2002)$ is equal to
  1. $1$
  2. $2$
  3. $3$
  4. $4$

Solution

We have, $ f(x)=\frac{\cos ^2 x+\sin ^4 x}{\sin ^2 x+\cos ^4 x} $ $\begin{aligned} & =\frac{1-\sin ^2 x+\sin ^4 x}{1-\cos ^2 x+\cos ^4 x} \\ & =\frac{1-\sin ^2 x\left(1-\sin ^2 x\right)}{1-\cos ^2 x\left(1-\cos ^2 x\right)} \\ & =\frac{1-\sin ^2 x \cos ^2 x}{1-\cos ^2 x \sin ^2 x}=1 \\ \therefore \quad f(2002) & =1\end{aligned}$

Asked in: AP EAMCET 2002

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