In two dimensions, the motion of a fluid (an incompressible and irrotational fluid) is governed by a velocity potential \( \varphi \). The velocity components of the fluid, \( u \) in the \( x \)-direction and \( v \) in the \( y \)-direction, are given by \( \langle u, v\rangle=\nabla \varphi \). Find the velocity components associated with the velocity potential \( \varphi(x, y)=3 \sin (\pi x) \sin (5 \pi y) \).