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If tan thita +sec thita = e^x then cos thuta = |
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Answer» cθ=e x ⇒ cosθ1+sinθ =e x ⇒ COS 2θ −sin 2θ cos 2θ +sin 2θ =e x (U\sin g COMPONENDO & DIVIDENDO rule)⇒tan 2θ = e x +1e x −1 as cosθ= 1+tan 2 2θ 1−tan 2 2θ ⇒cosθ= 1+( e x +1e x −1 ) 2 1−( e x +1e x −1 ) 2 ⇒cosθ= e 2x +12e x ⇒cosθ= e x +e −x 2 .OPTION B |
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