Use the formula \(\sin a-\sin b=2 \cos ((a+b) / 2) \sin ((a-b) / 2)\) to show that \(D_{N}(x) \sin (x / 2)=\frac{1}{2} \sin \left(N+\frac{1}{2}ight) x\). This proves (28.11).

Equation 28.11

Transcribed Image Text:

Dy(x)= sin (N+1)x 2 sin(x/2) (28.11)