2道三角函数的题目,
1.在三角形ABC中,已知(sinC)^2-(sinA)^2=sinA*sinB,sinA+sinC=2sinBcos(A/2),求角A,B,C
2.求证:(cosα)^2+(cosβ)^2-2cosαcosβcos(α+β)=(sin(α+β))^2