

CMR:
1) [tex]Cos\left ( \alpha -\frac{\Pi }{2}\right )[/tex] + Sin(anpha -bi) =0
2) Cho tam giác ABC. CMR: Cos(A + B) = Cos C
Mn giúp mh nha!!!!!!!!!![/tex][/tex]
1) [tex]Cos\left ( \alpha -\frac{\Pi }{2}\right )[/tex] + Sin(anpha -bi) =0
2) Cho tam giác ABC. CMR: Cos(A + B) = Cos C
Mn giúp mh nha!!!!!!!!!![/tex][/tex]