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If \(\sin x+\sin ^2 x=1, x \in\left(0, \frac{\pi}{2}\right)\), then \(\left(\cos ^{12} x+\tan ^{12} x\right)+3\left(\cos…

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If \(\sin x+\sin ^2 x=1, x \in\left(0, \frac{\pi}{2}\right)\), then \(\left(\cos ^{12} x+\tan ^{12} x\right)+3\left(\cos ^{10} x+\tan ^{10} x+\cos ^8 x+\tan ^8 x\right)+\left(\cos ^6 x+\tan ^6 x\right)\) is equal to:

[JEE Main 2025]

a

2

b

4

c

3

d

1

✓ Correct answer: a)

2

Explanation

\(\sin x+\sin ^2 x=1\)

\(\Rightarrow \sin x=\cos ^2 x\) and \(\tan x=\cos x\)

Given expression becomes

\(=2 \cos ^{12} x+6\left[\cos ^{10} x+\cos ^8 x\right]+2 \cos ^6 x\)

\(=2\left[\sin ^6 x+3 \sin ^5 x+3 \sin ^4 x+\sin ^3 x\right]\)

\(=2 \sin ^3 x\left[(\sin x+1)^3\right]\)

\(=2\left[\sin ^2 x+\sin x\right]^3\)

\(=2\)

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