The coefficient of active earth pressure for a loose sand having an angle of internalfriction '$$\phi$$' is

A

$$\frac{1 - \sin \frac{\phi}{2}}{1 + \sin \frac{\phi}{2}}$$

B

$$\frac{1 + \sin \frac{\phi}{2}}{1 - \sin \frac{\phi}{2}}$$

C

$$\frac{1 - \sin \phi}{1 + \sin \phi}$$

D

$$\frac{1 + \sin \phi}{1 - \sin \phi}$$