(cos x)^(y)=(cos y)^(x)

If tan(7x^(@))=(sin x^(@)cos y^(@)+cos x^(@)sin y^(@))/(cos x^(@)cos y^(@)-sin x^(@)sin^(@)) where x+y=134^(@) ,then the least positive integral value of x, is-

cos4x-cos4y = 8 (cos x-cos y) (cos x + cos y) (cos x-sin y) (cos x + sin y)

Prove that (i) 2 cos x cos y=cos (x+y)+cos (x-y) (ii) -2 . sin x sin y=cos (x+y)-cos (x-y) (iii) 2 sin x cos y=sin (x+y)+sin (x-y) (iv) 2 cos x sin y=sin (x+y)-sin (x-y)

Prove that, cos 4 x - cos4 y = 8(cos x - cos y)(cos x + cos y)(cos x - sin x)(cos x + sin y)

What is the value of {sin (x+y) -2 sin x+ sin(x-y)} /[cos (x-y) +cos (x+ y)-2 cos x] xx [(sin 10x- sin 8x)/ (cos-10x + cos 8x)] ? {[sin (x+y] -2 sin x+ sin(x-y)}//[cos (x-y) +cos (x+ y)-2 cos x]} xx [(sin 10x-sin 8x)//(cos10x + cos 8x)] का मान क्या है?

Given that cos(x-y) +cos (y-z) +cos (z-x)=-3/5 find cos x+ cos y + cos z

Prove that (sin x-sin y)/(cos x+cos y)=tan ((x-y)/2) .

Prove that :(sin x-sin y)/(cos x+cos y)=tan((x-y)/(2))

Prove that :(sin x+sin y)/(cos x+cos y)=tan((x+y)/(2))