tan^4 theta-tan^2theta=1 or tan^4 theta=tan^2theta+1 or tan^4 theta = sec^2theta or sin^4 theta/cos^4 theta=1/cos^2theta or
sin^4 theta/cos^2 theta=1 or cos^2theta/sin^4theta=1
cot^4 theta+cot^2theta=cot^2theta(1+cot^2theta)
= cot^2theta*csc^2theta= cos^2theta/sin^2theta*1/sin^2 theta
=cos^2theta/sin^4 theta= 1
:. cot^4 theta+cot^2theta=1 [Ans]