Question

28. If sinx + sin y= a and cos x + cos y =b, show that.....(in the photo)​

Answer 1

(1)

SOLUTION:-

RHS

= 2ab/ (a²+b²)

2(sinx+siny) ( cosx+cosy)

= -----------------------------------------

(sinx+siny)²+ (cosx+cosy)²

2(sinxcosy+cosxsiny)(sinxcosx+sinycosy) = -----------------------------------------------------

2+2sinxsiny+2cosxcosy

[sin(x+y)( sin2x+sin2y)]

= -------------------------------------

2[1+cos(x-y)]

Sorry