Question

PT cos alpha +cos (alpha+120) + cos (alpha-120)
= 0​

Answer 1

Answer:

Reason: we can write cos( 120) as cos(90+30) and this will give us -sin (30) ,similarly by using this rule and the formulae for

sin(A+B) =sinA cosB+ cosA sinB

Ans sin (A-B) = sinAcosB-cosAsinB

If you evaluate they will cancel each other and the value will be 0