Identitas trigonometri (Tan delta + cot delta) cos^2 delta = cot delta

Trigonometry.

[tex]\displaystyle \left ( \tan \Delta + \cot \Delta \right )\cos^2 \Delta \\ =\left ( \frac{\sin \Delta }{\cos \Delta }+\frac{\cos \Delta }{\sin \Delta } \right )\cos^2 \Delta\\ =\left (\frac{\sin^2 \Delta +\cos^2 \Delta }{\sin \Delta \cos \Delta } \right )\cos^2 \Delta\\ =\frac{1(\cos \Delta )}{\sin \Delta }=\cot \Delta [/tex]
Proved.