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Question

Question: \((2n + 1)\frac{\pi}{2}\)then (rc) \(n = - 2, - 1,0,1,2\)...

(2n+1)π2(2n + 1)\frac{\pi}{2}then (rc) n=2,1,0,1,2n = - 2, - 1,0,1,2

A

\therefore

B

x=3π4,π4,π4,3π4,5π4x = \frac{- 3\pi}{4},\frac{- \pi}{4},\frac{\pi}{4},\frac{3\pi}{4},\frac{5\pi}{4}

C

3π2,π2,π2,3π2,5π2\frac{- 3\pi}{2},\frac{- \pi}{2},\frac{\pi}{2}, ⥂ \frac{3\pi}{2},\frac{5\pi}{2}

D

None of these

Answer

x=3π4,π4,π4,3π4,5π4x = \frac{- 3\pi}{4},\frac{- \pi}{4},\frac{\pi}{4},\frac{3\pi}{4},\frac{5\pi}{4}

Explanation

Solution

We have (2n±1)π4(2n \pm 1)\frac{\pi}{4}

or 2tanx+1tan2x1+tan2x=tanx\frac{2\tan x + 1 - \tan^{2}x}{1 + \tan^{2}x} = \tan x

\Rightarrow tan3x+tan2xtanx1=0\tan^{3}x + \tan^{2}x - \tan x - 1 = 0,

(tan2x1)(tanx+1)=0\Rightarrow (\tan^{2}x - 1)(\tan x + 1) = 0

x=mπ±π4\Rightarrow x = m\pi \pm \frac{\pi}{4}

Now put n=0n = 0

θ=π2θ=π4\theta = - \frac{\pi}{2}\theta = \frac{\pi}{4}and rr

Since \therefore, therefore sinθ=12,32\sin\theta = \frac{1}{2}, - \frac{3}{2} only.