If sin A, cos A and tan A are in geometric progression, then cot6Aācot2 A is equal to
-1
0
1
None of these
Since sin A, cos A and tan a are in G.P., we have
cos2A=sin A tan A⇒cos3 A=sin2A⇒cot2A=sec A⇒cot4 A=1+tan2A⇒cot6 A−cot2=1