7.sin(3/4π+β)=5/13,则sin(π/4-β)=5/13cos(π/4-a)=cos(a-π/4)=3/5,则cos(a-β)=cos(a-π/4+π/4-β)=cos(a-π/4)cos(π/4-β)-sin(π/4-β)sin(a-π/4)=然后算即可8.tan(a-π/3)=跟据公式展开解方程即可9.与第...