Question 416006


cot^2y(sec^2y-1)=1

.use identites cot^2y = 1/tan^2y and  sec^2y-1 = tan^2y



cot^2y(sec^2y-1) = (1/tan^2y)(tan^2y) <--The tan^2y cancels out

cot^2y(sec^2y-1)= 1