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Question

Question: If \(\tan\theta = t,\) then \(\tan 2\theta + \sec 2\theta =\)...

If tanθ=t,\tan\theta = t, then tan2θ+sec2θ=\tan 2\theta + \sec 2\theta =

A

1+t1t\frac{1 + t}{1 - t}

B

1t1+t\frac{1 - t}{1 + t}

C

2t1t\frac{2t}{1 - t}

D

2t1+t\frac{2t}{1 + t}

Answer

1+t1t\frac{1 + t}{1 - t}

Explanation

Solution

tan2θ=2tanθ1tan2θ,cos2θ=1tan2θ1+tan2θ\tan 2\theta = \frac{2\tan\theta}{1 - \tan^{2}\theta},\cos 2\theta = \frac{1 - \tan^{2}\theta}{1 + \tan^{2}\theta}

tan2θ+sec2θ=2t1t2+1+t21t2=(1+t)2(1t)(1+t)=1+t1t\tan 2\theta + \sec 2\theta = \frac{2t}{1 - t^{2}} + \frac{1 + t^{2}}{1 - t^{2}} = \frac{(1 + t)^{2}}{(1 - t)(1 + t)} = \frac{1 + t}{1 - t}.