\[(a)\;\frac{v}{2} \sqrt {1+ 2 \cos^2 \theta} \quad (b)\;\frac{v}{2} \sqrt {1+ 2 \sin ^2 \theta} \quad (c)\;\frac{v}{2} \sqrt {1+ 3 \cos^2 \theta} \quad (d)\;v \cos \theta \]
