If two vectors \( \vec{A} \) and \( \vec{B} \) having equal magnitude \( R \) are inclined at an angle \( \theta \), then:
\( |\vec{A} + \vec{B}| = 2R \cos\left(\dfrac{\theta}{2}\right) \)
\( |\vec{A} - \vec{B}| = 2R \cos\left(\dfrac{\theta}{2}\right) \)
\( |\vec{A} + \vec{B}| = 2R \sin\left(\dfrac{\theta}{2}\right) \)
\( |\vec{A} - \vec{B}| = \sqrt{2}\,R \sin\left(\dfrac{\theta}{2}\right) \)