已知sin(派+α)=m,则sin(3派-α)= 已知cosα=7分之派,且α∈[-派,0],则角α=

问题描述:

已知sin(派+α)=m,则sin(3派-α)= 已知cosα=7分之派,且α∈[-派,0],则角α=

sin(π+α)=m
sin(3π-α)=sin{2*2π-(π+α)} = -sin(π+α) = -m
cosα=π/7>0
α∈[-π,0]
α = -arccos(π/7)