tanA+cotA bằng bao nhiêu

\(\tan \alpha=\dfrac{\sin\alpha}{\cos\alpha}\\\cot\alpha=\dfrac{\cos\alpha}{\sin\alpha}\\→\tan \alpha+\cot\alpha=\dfrac{\sin\alpha}{\cos\alpha}+\dfrac{cos\alpha}{\sin\alpha}\\=\dfrac{\sin^2\alpha+\cos^2\alpha}{\sin\alpha.\cos\alpha}\\=\dfrac{1}{\dfrac{1}{2}.2\sin\alpha\cos\alpha}\\=\dfrac{1}{\dfrac{1}{2}.\sin 2\alpha}\\=\dfrac{2}{\sin 2\alpha}\)