The level curves of two functions [math]u\left(x,y\right)=y^3-3x^2y+x[/math] and [math]v\left(x,y\right)=x^3-3xy^2+y[/math].[br]Blue represents [math]u[/math] and red represents [math]v[/math]. Since [math]u[/math] and [math]v[/math] are both harmonic and [math]v[/math] is a harmonic conjugate of [math]u[/math], the level curves of [math]u[/math] and [math]v[/math] intersect each other at right angles.