Step 1 :Draw the preimage of a triangle with coordinates $T(2,1)$, $U(0,-1)$, and $V(3,-3)$.
Step 2 :Reflect the triangle across the line $y=x$. This involves swapping the x and y coordinates of each point.
Step 3 :The coordinates of the reflected triangle are $T^{\prime}(1, 2)$, $U^{\prime}(-1, 0)$, and $V^{\prime}(-3, 3)$.
Step 4 :\[\boxed{\begin{array}{ll} T^{\prime}(1, 2) \\ U^{\prime}(-1, 0) \\ V^{\prime}(-3, 3) \end{array}}\]