Question 230149
1/1-cos^2x=1+cot^2x 


L.H.S
1/1-cos^2x 
By using sin^2x+cos^2x=1
1/sin^2x 
try to make cos^2x/sin^2x since it equals to cot^2x
(1/(sin^2x)*(cos^2x/(cos^2x)
(cos^2x/sin^2x)*(cos^2x)
cot^2x+1 (proven)


there might be more easier way to prove it.