For the other direction, take......
We pause to record a generalization of Theorem 2 in a different direction.
Proceeding further in this direction, we obtain the following corollary.
Let A denote the rectangle B rotated through π/6 in a clockwise direction about the vertex (0,1).
The method of proof of Theorem B can be adapted to extend the right-to-left direction of Mostowski's result by showing that......
the derivative of f at x in direction v
a direction pointing downward with respect to τ
inequality in the opposite direction