यदि $\alpha, \beta, \gamma$ कोई भी तीन कोण हैं,तो $\cos \alpha + \cos \beta - \cos \gamma - \cos (\alpha + \beta + \gamma) =$

• A
  $4 \cos \frac{\alpha+\beta}{2} \cos \frac{\beta+\gamma}{2} \cos \frac{\gamma+\alpha}{2}$
• B
  $4 \cos \frac{\alpha+\beta}{2} \sin \frac{\beta+\gamma}{2} \sin \frac{\gamma+\alpha}{2}$
• C
  $4 \cos \frac{\alpha+\beta}{2} \sin \frac{\beta-\gamma}{2} \sin \frac{\gamma-\alpha}{2}$
• D
  $4 \sin \frac{\alpha+\beta}{2} \cos \frac{\beta+\gamma}{2} \cos \frac{\gamma+\alpha}{2}$