Question

Докажите тождество:
Cos(l+b)+sin(-l)sin(-b)=cos l cos b

Answer 1

1)sin(l+b)+sin(l-b)=2sinlcosb;
2)cos(l+b)+cos(l-b)=2coslccosb;
3)sin(l+b)+sin(l-b)/cos(l+b)+cos(l-b)=2sinlcosb/2coslccosb=sinl/cosl=tgl.