Tìm góc lượng giác $x$ sao cho:

cos(x + 50°) = $\frac{1}{2}$;

Do $\cos 60^\circ = \frac{1}{2}$ nên cos(x + 50°) = $\frac{1}{2}$⇔ cos(x + 50°) = cos 60°

$\Leftrightarrow \left[ \begin{array}{l}x + 50^\circ = 60^\circ + k360^\circ \\x + 50^\circ = - 60^\circ + k360^\circ \end{array} \right.\left( {k \in \mathbb{Z}} \right)$

$\Leftrightarrow \left[ \begin{array}{l}x = 10^\circ + k360^\circ \\x = - 110^\circ + k360^\circ \end{array} \right.\left( {k \in \mathbb{Z}} \right)$.