Question

( Rightarrow frac{cos 9 x-cos 5 x}{sin 17 x-sin 3 x}=frac{sin 2 x}{cos 10 x} )
LHSt. We know ldenth'ty
Licos ( A-cos B=-2 sin left(frac{a+b}{2}right) sin left(frac{a-b}{2}right) )
ii, ( sin A-sin B=2 cos left(frac{a+b}{2}right) sin left(frac{a-b}{2}right) )
( therefore quad angle H S H frac{-2 sin T x times sin 2 x}{2 cos 10 x sin 1 x} geqslant frac{sin 2 x}{cos 10 x} )
Pro

# cos 9x - cos 5x sin 17x - sin 3x -=- sin 2x cos 10x

Solution