Parametric Curves

The parametric equations
x = vt \cos \theta,
y = vt \sin \theta - \frac{1}{2} gt^2,
describe the path of a projectile fired at an angle of $\theta,$ where $v$ is the initial velocity, $g$ denotes acceleration due to gravity, and $t$ denotes time.

The path itself is a parabolic arch, and the distance the projectile reaches varies with the angle $\theta.$  Find the maximum distance.