Question

cho cot=2. CM

MỌI NGƯỜI GIÚP EM VS Ạ :)))

Answer 1

ta có:\(\cot\alpha=2\Rightarrow\dfrac{cos\alpha}{sin\alpha}=2\Rightarrow\dfrac{\cos^2\alpha}{\sin^2\alpha}=4\Rightarrow\cos^2\alpha=4\sin^2\alpha\)

\(\Rightarrow\dfrac{sin^2\alpha-\cos^2\alpha}{sin^2\alpha+\cos^2\alpha}=\dfrac{sin^2\alpha-4sin^2\alpha}{sin^2\alpha+4sin^2\alpha}=\dfrac{-3sin^2\alpha}{5sin^2\alpha}=-\dfrac{3}{5}\left(ĐPCM\right)\)