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=

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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=

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=
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=

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)

sin(派+α)=-sina=m sina=-m
sin(3派-α)=sin(派-α)=sina=-m

sin(π+a)=-sina=m,则Sina=-m
sin(2π+a)=sina
Sin(3π-a)=Sin(2π+π-a)=sin(π-a)=Sina=-m


α∈[-派,0],则Sina<0
Sina^2+Cosa^2=1
所以Sina=(4根号3)π/7