Answer:
steps below
Step-by-step explanation:
It's easier to prove from right side to left side. If you insist to prove from left to right, you can just reverse the calculation from bottom to the top.
[tex]cot^{2} a * cos^{2}a \\= cot^{2} a * (1-sin^{2} a)\\= cot^{2} a - cot^{2} a*sin^{2} a\\= cot^{2} a - \frac{cos^{2} a}{sin^{2}a} *sin^{2} a\\= cot^{2} a - cos^{2} a[/tex]
