Answer 1

$\tg x+ \frac{1}{ \cos x } = 2 \sin x \\ \frac{ \sin x + 1}{ \cos x } = 2 \sin x \\ \sin x + 1 = 2 \sin x \cos x \\ \sin x + 1 = \sin 2x \\ \sin x - \sin 2x = - 1 \\ 2\sin \frac{x - 2x}{2} \cos \frac{x + 2x}{2} = - 1\\ 2 \sin \frac{x}{2} \cos \frac{3x}{2} = 1$

дальше не знаю как

Answer 2

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