JEE Physics Practice Question

If two vectors $$\vec{A}$$ and $$\vec{B}$$ having equal magnitude $$R$$ are inclined at angle $$\theta$$, then

1. A.$$|\vec{A}+\vec{B}|=2 R \cos \left(\frac{\theta}{2}\right)$$
2. B.$$|\vec{A}-\vec{B}|=2 R \cos \left(\frac{\theta}{2}\right)$$
3. C.$$|\vec{A}-\vec{B}|=\sqrt{2} R \sin \left(\frac{\theta}{2}\right)$$
4. D.$$|\vec{A}+\vec{B}|=2 R \sin \left(\frac{\theta}{2}\right)$$