Find the value of cot3A-3cotA/3 cot2A-1

Find the value of cot³A-3cotA/3 cot2A-1

(a) cot²2A + tan²A

(b) tan²2A + cot²A

(c) tan3A

(d) cot3A

Sol:

As we know that: tanA + tanB + tanC = tanA tanB tanC

Sin2A + sin2B + sin2C = 4 sinA sinB sinC