(a) Show that for a projectile the angle between the velocity and the x - axis as a function of time is given by
`theta(t)="tan"^(-1)((v_(0y)-"gt")/(v_(@)x))`
(b) Shows that the projection angle `theta_(@)` for a projectile launched from the origin given by
`theta_(0)=tan^(-1)((4h_(m))/(R))`
where the symbols have their usual meaning.