Assume this is 22 degrees from the horizontal (x). A vector can always be split into components - in this case we can think of the world in two dimensions, meaning the 72ms-1 has a vertical and a horizontal component. We therefore know the hypotenuse of the triangle (the overall velocity) and the angle from the ground. Hence we can use trigonometry to solve this problem.
We know x and the hypotenuse, and we want to know the magnitude of the adjacent side (horizontal), therefore we can use cosx=adj/hyp
