#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]