Cho sinα = \(\frac{3}{5}\), cosα = \(\frac{4}{5}\)

----- Nội dung ảnh -----
Ví dụ 4. Cho sinα = \(\frac{3}{5}\), Tìm A

\[ A = \sin(90^\circ - \alpha) + \sin(180^\circ - \alpha) + \cos(180^\circ - \alpha) \]
\[ = \tan(90^\circ - \alpha) + 3\cot(180^\circ - \alpha) + \tan(90^\circ + \alpha) \]