sin (pai-x)=24/25 则cos(x/2)=?
问题描述:
sin (pai-x)=24/25 则cos(x/2)=?
答
sin(π-x)=24/25
sin(x)=24/25
cos^2(x)=1-sin(x)^2=49/625
cos(x)=+-7/25
cos^2(x/2)=(1+cos(x))/2=9/25或16/25
cos(x/2)=+-3/5或+-4/5