Theorem 5.2.1 Triangle Area Formula

Lines a, b and c are parallel lines.
Look at triangle ABC. Drag around the vertex, C and notice that the area does not change.
Answer the following questions:
What are the sides of the triangle?
Which sides change as you drag around vertex C?
What is the area formula for a triangle?
What happens to the area when you move vertex C? Why?
Do the same for triangle ABD (dragging around vertex D). What do you notice?

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Christy Bredestege, Created with GeoGebra