How do you use the fundamental identities to prove other identities?

1 Answer
Feb 22, 2015

Divide the fundamental identity sin^2x + cos^2x = 1sin2x+cos2x=1 by sin^2xsin2x or cos^2xcos2x to derive the other two:

sin^2x/sin^2x + cos^2x/sin^2x = 1/sin^2xsin2xsin2x+cos2xsin2x=1sin2x

1 + cot^2x = csc^2x1+cot2x=csc2x

sin^2x/cos^2x + cos^2x/cos^2x = 1/cos^2xsin2xcos2x+cos2xcos2x=1cos2x

tan^2x + 1 = sec^2xtan2x+1=sec2x