sinX=1/3 ,cos(2X - π)=
问题描述:
sinX=1/3 ,cos(2X - π)=
答
cos(2x- π)= cos 2(x-π/2)=2*【cos(x-π/2) 】^2 -1 = 2 * (sin x )^2 -1 = - 7/9.
sinX=1/3 ,cos(2X - π)=
cos(2x- π)= cos 2(x-π/2)=2*【cos(x-π/2) 】^2 -1 = 2 * (sin x )^2 -1 = - 7/9.