Mathematics · 2020
JEE Main · 9 January 2020, Shift 2 · Q69
If x=Σ_n=0^∞(-1)^n tan^2 n θ and y=Σ_n=0^∞ cos^2 n θ, for 0<θ<(π)/4, then:
If $\displaystyle x=\sum_{n=0}^{\infty}(-1)^n \tan ^{2 n} \theta$ and $\displaystyle y=\sum_{n=0}^{\infty} \cos ^{2 n} \theta$,
for $\displaystyle 0<\theta<\frac{\pi}{4}$, then :
Official answer
(2)
$\displaystyle y(1-x)=1$
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JEE Main 2020 Mathematics question, with the answer from NTA’s final answer key. Where our answers come from.