If `A+B+C=180^(@)` then the value of `cosec A(sin B cos C+cos B sin C)` is

If cos A+cos B+cos C=0sin A+sin B+sin C=0 and A+B+C=180^(@), then the value of cos3A+cos3B+cos3C is

If sin A+sin B + sin C =3, then the value of cos A + cos B + cos C is

If A+B+C=0, then the value of sin^(2)A+cos C(cos A cos B-cos C)+cos B(cos A cos C-cos B) is equal to: -1 (b) 0(c)1 (d) none of these

If A+B+c=180^(@), then sec A(cos B cos C-sin B sin C) is equal to 0 b.-1 c.1d .none of these

If A+B+C=180^(@), prove that sin2A+sin2B-sin2C=4cos A cos B sin C