Question

$\sqrt{2} \cos(x) - 1 = 0$
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Answer 1

$\sqrt{2} cos \: x \: - 1 = 0 \\ \sqrt{2} cos \: x \: = 1 \\ cos \: x \: = \frac{1}{ \sqrt{2} } \\ x = \frac{\pi}{4} + 2\pi \: k \\ x = - \frac{\pi}{4} + 2\pi \: k$

Ответ: х = ± π/4 + 2πk, k = 0, 1, 2, ...