Question

y=sin^2x+cos^2x y=1定义域为何不同

Answer 1

1、cos2x = (cosx)^x - (sinx)^x = 2(cosx)^2-1 = 1- 2(sinx)^x

y=（sinx)^2+(cosx)^2 = (1-cos2x)/2 + (1+cos2x)/2.

定义域为-π + 2Kπ