DẠNG 3. PHƯƠNG TRÌNH LƯỢNG GIÁC

A. \(\cos x = \cos \alpha \Leftrightarrow x = \alpha + k2\pi ,k \in \mathbb{Z}.\) 

B. \(\cos x = \cos \alpha \Leftrightarrow x = - \alpha + k2\pi ,k \in \mathbb{Z}.\) 

C. \(\cos x = \cos \alpha \Leftrightarrow \left[ {\begin{array}{*{20}{l}}{{\rm{x}} = \alpha + {\rm{k}}2\pi }\\{{\rm{x}} = \pi - \alpha + k2\pi }\end{array},k \in \mathbb{Z}} \right..\) 

D. \(\cos x = \cos \alpha \Leftrightarrow \left[ {\begin{array}{*{20}{l}}{{\rm{x}} = \alpha + {\rm{k}}2\pi }\\{{\rm{x}} = - \alpha + {\rm{k}}2\pi }\end{array},{\rm{k}} \in \mathbb{Z}} \right..\)

A. \(\tan x = \tan \alpha \Leftrightarrow x = \alpha + k\pi ,k \in \mathbb{Z}.\) 

B. \(\tan x = \tan \alpha \Leftrightarrow x = \pi - \alpha + k\pi ,k \in \mathbb{Z}.\) 

C. \(\tan x = \tan \alpha \Leftrightarrow \left[ {\begin{array}{*{20}{l}}{x = \alpha + k2\pi }\\{x = \pi - \alpha + k2\pi }\end{array},k \in \mathbb{Z}} \right..\) 

D. \(\tan x = \tan \alpha \Leftrightarrow \left[ {\begin{array}{*{20}{l}}{x = \alpha + k2\pi }\\{x = - \alpha + k2\pi }\end{array},k \in \mathbb{Z}} \right..\)

A. \(\cot x = \cot \alpha \Leftrightarrow x = \alpha + k\pi ,k \in \mathbb{Z}.\) 

B. \(\cot x = \cot \alpha \Leftrightarrow x = \pi - \alpha + k\pi ,k \in \mathbb{Z}.\) 

C. \(\cot x = \cot \alpha \Leftrightarrow \left[ {\begin{array}{*{20}{l}}{x = \alpha + k2\pi }\\{x = \pi - \alpha + k2\pi }\end{array},k \in \mathbb{Z}} \right..\) 

D. \(\cot x = \cot \alpha \Leftrightarrow \left[ {\begin{array}{*{20}{l}}{x = \alpha + k2\pi }\\{x = - \alpha + k2\pi }\end{array},k \in \mathbb{Z}} \right..\)