Does this triangle-area theorem have a name?

Question

Given two distinct parallel lines and two distinct fixed points on one of the lines and a point that can vary on the other line. Then the areas of all the triangles formed by those 3 points are all equal. – Does this theorem have a name? I am not asking for an explanation of the mathematics, but simply an elevator-pitch name, something that rolls off the tongue more smoothly than "Do you know the area = one half base times height theorem?"

Answer 1

It is a simply application of the formula for the area of the triangle that is

$$S=\frac12\cdot AB \cdot d$$

where $AB$ is the length of the segment between the two fixed point and $d$ is the distance between the two lines.

That property can be viewd also as a particular case of Cavalieri's Principle

Answer 2

This is a particular case of Euclid's Proposition 38 from Book I of the Elements:

Triangles which are on equal bases and in the same parallels equal one another.

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[ EDIT ]   Credit goes to @Micah's comment for pointing out that this particular case makes in fact the object of Proposition I.37:

Triangles which are on the same base and in the same parallels equal one another.