Answer :
Always try to find a way to convert cotx, secx, cscx, and tanx into cosx and sinx
cotx (1/secx) = (1/sinx) - sinx
(cosx/sinx) (cosx) = (1/sinx) - sinx
cos²x / sinx = (1- sin²x)/sinx
cos²x = 1 - sin²x
sin²x + cos²x = 1
cotx (1/secx) = (1/sinx) - sinx
(cosx/sinx) (cosx) = (1/sinx) - sinx
cos²x / sinx = (1- sin²x)/sinx
cos²x = 1 - sin²x
sin²x + cos²x = 1