# A projectile's launch speed is five times its speed at maximum height.Find launch angle.How do I find this?

##### 1 Answer

Mar 11, 2018

#### Explanation:

If the angle of projection is

At the topmost point of the path, the projectile's vertical velocity component vanishes - and thus its velocity at that point is exactly horizontal, and its magnitude is

Thus $u = 5u cos alpha implies cos alpha = 1/5#