An idealized model of a river flowing around a rock considersa
circular rock of radius 1 in the river, which flows across
thexy-plane in the positive x0direction. the model begins with
thepotential funtion

where

show that the flow of v is tangent to the circle
meaning that now water crosses thecircle.

doing the gradient is easy but im not sure about proving that
theflow is tangent to the equation of the rock.