If cos y=x cos (a+y),cos a≠1 prove that dydx=cos2(a+y)sin a
cos y=x cos(a+y)⇒x=cos ycos(a+y)dxdy=ddy[cos ycos(a+y)]=cos(a+y)sin y+cos ysin(a+y)cos2(a+y)dxdy=sin(a+y−y)cos2(a+y)dxdy=sin acos2(a+y)⇒dxdy=cos2(a+y)sin a
If cos y=x cos (a+y),with cos a≠1,prove that dydx=cos2(a+y)sin a.