Chứng minh : tan6a – tan4a – tan 2a= tan6a. tan4a . tan2a Giúp mình với 22/08/2021 Bởi Faith Chứng minh : tan6a – tan4a – tan 2a= tan6a. tan4a . tan2a Giúp mình với
$\begin{array}{l}\tan 6a = \tan \left( {4a + 2a} \right) = \dfrac{{\tan 4a + \tan 2a}}{{1 – \tan 4a.\tan 2a}}\\ \Rightarrow \tan 6a\left( {1 – \tan 4a.\tan 2a} \right) = \tan 4a + \tan 2a\\ \Leftrightarrow \tan 6a – \tan 4a – \tan 2a = \tan 2a.\tan 4a.\tan 6a\end{array}$ Bình luận
$\begin{array}{l}
\tan 6a = \tan \left( {4a + 2a} \right) = \dfrac{{\tan 4a + \tan 2a}}{{1 – \tan 4a.\tan 2a}}\\
\Rightarrow \tan 6a\left( {1 – \tan 4a.\tan 2a} \right) = \tan 4a + \tan 2a\\
\Leftrightarrow \tan 6a – \tan 4a – \tan 2a = \tan 2a.\tan 4a.\tan 6a
\end{array}$