已知sin(x+π/4)=4/5,cos(x+π/4)=-3/5,求sinx的值
问题描述:
已知sin(x+π/4)=4/5,cos(x+π/4)=-3/5,求sinx的值
答
√2/2(sinx+cosx)=4/5
√2/2(cosx-sinx)=-3/5
√2sinx=7/5
sinx=7√2/10