Question

to show sin (90-A) sin(180+A) +cos(90+A) cos(180-A)=0​

Answer 1

Step-by-step explanation:

sin(90-A)=cosA

sin(180+A)= -sinA

cos(90+A)= -sinA

cos(180-A)= -cosA

Putting all these values in the above expression,

=(cosA)(-sinA) + (-sinA)(-cosA)

= -cosAsinA+cosAsinA

=0

Hence, proved.