Question

函数y=cosx^4-sinx^4的最小正周期

Answer 1

y=cosx^4-sinx^4

= (cosx ^2 + sinx ^2) (cosx ^2 - sinx^2)

= 1 * (cosx ^2 - sinx ^2)

= cosx ^2 - sinx ^2

= cos(2x)

所以最小正周期为

T = 2π/2 = π