Question 829188
cot^2(x)-cot^2(x)*cos^2(x) 
-----
Factor out the cot^2(x) to get:
= cot^2(x)[1 - cos^2(x)]
= [cos^2(x)/sin^2(x)][sin^2(x)]
= cos^2(x)
====================

I am told to first factor, then use the fundamental identities to determine which of the following values our expression is NOT equivalent to.
sin^2((pi/2)-x):::: yes
tan^(2)a::: not
cos^(2)x::: yes
1/sec^(2)x::: yes
1-sin^(2)x::: yes
-------------------------
Cheers,
Stan H.