الف) $\sin \theta (\tan \theta + \cot \theta) = 1$

ب) $(\sin \theta + \cos \theta - 1)(\sin \theta + \cos \theta + 1) = 2 \sin \theta \cos \theta$

ج) $\frac{1}{1 + \cos \theta} + \frac{1}{1 - \cos \theta} = 2 \cot^2 \theta$

د) $2 \tan \theta + \frac{2}{1 + \tan^2 \theta} = 2 \sin \theta \cos \theta$