Đáp án:
\(\left[ \begin{array}{l}
\cos a = \dfrac{1}{2}\\
\cos a = - \dfrac{1}{2}
\end{array} \right. \to \left[ \begin{array}{l}
\tan a = \sqrt 3 \\
\tan a = - \sqrt 3
\end{array} \right.\)
Giải thích các bước giải:
\(\begin{array}{l}
\sin a = \dfrac{{\sqrt 3 }}{2}\\
{\sin ^2}a + {\cos ^2}a = 1\\
\to \dfrac{3}{4} + {\cos ^2}a = 1\\
\to {\cos ^2}a = \dfrac{1}{4}\\
\to \left[ \begin{array}{l}
\cos a = \dfrac{1}{2}\\
\cos a = - \dfrac{1}{2}
\end{array} \right. \to \left[ \begin{array}{l}
\tan a = \sqrt 3 \\
\tan a = - \sqrt 3
\end{array} \right.\\
\to \left[ \begin{array}{l}
\cot a = \dfrac{1}{{\sqrt 3 }}\\
\cot a = - \dfrac{1}{{\sqrt 3 }}
\end{array} \right.
\end{array}\)
