To `cos(A+B)=cosx.cosy - sin x sin "and hence find "cos75^(@)`

Prove geometrically that cos(x + y) = cos x cos y - sinx sin y and hence prove cos((pi)/(2) + x) = - sin x .

Prove Geometrically cos(x+y)=cosx,cosy-sinx.siny and hence prove that cos(x-y)= cosxcosy+sinxsiny using unit circle concept ?

(a)Derive geometrically that cos(x+y)=cos x cos y-sin x sin y .Hence deduce the valueof cos 75^@

sin(A+B)=sinA cos B +cos A sin B

Prove that (sin 3 theta)/(1+2cos2 theta)=sin theta and hence find sin15^(@)

Prove that (sin 3 theta)/(1+2cos2 theta)=sin theta and hence find sin15^(@)

If y=(sin x+cos x)/(sin x- cos x)" find " (dy)/(dx) .