已知0<β<π/4<α<3π/4,cos(π/4-α)=3/5,sina(3π/4+β)=5/13,求sina(α+β)的值
问题描述:
已知0<β<π/4<α<3π/4,cos(π/4-α)=3/5,sina(3π/4+β)=5/13,求sina(α+β)的值
答
0<β<π/4<α<3π/4
可知-
-π/2