Prove that: `(cos9x-cos5x)/(sin 17 x-sin3x)=\ -(sin2x)/(cos 10 x)`

Explanation

`LHS=frac{cos 9 x-cos 5 x}{sin 17 x-sin 3 x}=frac{-2 sin (frac{9 x+5 x}{2}) sin (frac{9 x-5 x}{2})}{2 cos (frac{17 x+3 x}{2}) sin (frac{17 x-3 x}{2})}`



`=-frac{sin 7 x sin 2 x}{cos 10 x sin 7 x}`




`=-frac{sin 2 x}{cos 10 x}=` `RHS`




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