River width d = 100m, water speed V1 = 5m / s, ship speed V2 = 3m / s in still water, the shortest voyage of the ship across the river, the shortest voyage way to cross the river time

River width d = 100m, water speed V1 = 5m / s, ship speed V2 = 3m / s in still water, the shortest voyage of the ship across the river, the shortest voyage way to cross the river time

Brother, please draw a picture as I said. First of all, you need to know that speed is a vector. In addition, you need to know that ship speed in water = water speed + still water speed (both are vectors). First, draw a line with a length of 5cm, then draw a straight line on both sides parallel to it, and draw a circle with r = 3cm at the end of the line