यदि $P+Q+R=\frac{\pi}{4}$,तो $\cos \left(\frac{\pi}{8}-P\right)+\cos \left(\frac{\pi}{8}-Q\right)+\cos \left(\frac{\pi}{8}-R\right)=$

• A
  $4 \cos \frac{P}{2} \cos \frac{Q}{2} \cos \frac{R}{2}-\cos \frac{\pi}{8}$
• B
  $4 \cos \frac{P}{2} \cos \frac{Q}{2} \cos \frac{R}{2}+\cos \frac{\pi}{8}$
• C
  $4 \sin \frac{P}{2} \cos \frac{Q}{2} \cos \frac{R}{2}-\cos \frac{\pi}{8}$
• D
  $4 \sin \frac{P}{2} \cos \frac{Q}{2} \cos \frac{R}{2}+\cos \frac{\pi}{8}$