How to calculate the triangle rule of physics?

How to calculate the triangle rule of physics?

The movement of the parachute after falling for a certain period of time is uniform. When there is no wind, a parachute diver falls vertically, and the landing speed is 5m / s. now there is wind, and the wind can make him move eastward along the horizontal direction with a speed of 4m / s. how fast will he land? Draw a diagram of the speed composition! In short, it is the vertical speed and horizontal speed