Question

已知三角形ABC中的内角A,B,C的对边分别为a,b,c,定义向量m=(2sinB,-根号3),定量n=(cos2B,2

Answer 1

(1)m//n=>2sinB/(-√3 ) = cos2B/(2[cos(B/2)]^2-1)2sinB(2[cos(B/2)]^2-1) =-√3cos2Bsin2B = -√3cos2Btan2B = -√3B = π/3(2)b=2by sine-rulea/sinA = b/sinBa= (b/sinB)sinA = (4√3/3)sinAc= (b/sinB)sinC = (...