Prove that
sin(1500 + x) + sin (1500 – x) = cos x
In this question the following formula will be used:
Sin( A +B)= sinA cos B + cosA sinB
Sin( A - B)= sinA cos B - cosA sinB
= sin150 cosx + cos 150 sinx + sin150 cosx – cos150 sinx
=2sin150cosx
=2sin(90 + 60)cosx
=2cos60cosx
=2cosx
=cosx