Question

Cos(alpha+beta)=0
then........Sin(alpha+beta)=?

a)cos beta b)cos 2beta
c)sin alpha d)sin2alpha

(PROVIDE ANSWER WITH SOLUTION)

Answer 1

the right answer
b)cos 2beta
for solution
see photo

Answer 2

$cos( \alpha +  \beta )=0 \\ ( \alpha + \beta )=cos^{-1} 0 \\  \alpha + \beta =90^0}  \\  \alpha =90- \beta  \\  \alpha + \beta =(2 \alpha -90^{0} or (90^{0}-2 \beta ) \\ sin( \alpha + \beta )=sin(2 \alpha -90^{0})or sin(90-2 \beta ) \\ sin( \alpha + \beta )=cos2 \beta$