Question

Решите тригонометрическое уравнение :
sin(x+30°)=cos(x-30°)
x принадлежит (0 °; 180 °)

Answer 1

$\sin\left(x+30^\circ\right)=\cos\left(x-30^\circ\right)\medskip\\\sin x\cos 30^\circ+\cos x\sin 30^\circ=\cos x\cos 30^\circ+\sin x\sin 30^\circ\medskip\\\dfrac{\sqrt{3}}{2}\sin x+\dfrac{1}{2}\cos x=\dfrac{\sqrt{3}}{2}\cos x+\dfrac{1}{2}\sin x\medskip\\\dfrac{\sqrt{3}-1}{2}\sin x+\dfrac{1-\sqrt{3}}{2}\cos x=0\mid\,:\cos x\neq 0\medskip\\\dfrac{\sqrt{3}-1}{2}\mathrm{tg}\,x-\dfrac{\sqrt{3}-1}{2}=0\medskip\\\mathrm{tg}\,x=1$

$\begin{cases}\mathrm{tg}\,x=1\smallskip\\x\in\left(0^\circ\,;\,180^\circ\right)\end{cases}\Leftrightarrow x=45^\circ$

Ответ. $x=45^\circ$