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