Question

Show that a boat must move at an angle if 90' with respect to river water in order to cross the river in a minimum time?​

Answer 1

Answer:

To cross the river in shortest time boat must be rowed along the width of river i.e., boat must be rowed perpendiculat to the bank of 90∘ with the flow of water . because width of river is the shortest distance . so velocity must be taken in that direction to obtain shortest time