The Sum of the Interior Angles of Any Triangle
- Author:
- Irina Boyadzhiev
Consider this triangle made out of two-sided blue and yellow origami paper.
- Drag the blue vertices to adjust the shape of the triangle.
- Click the “Fold” button. This will color the lower left vertex yellow.
- Drag the the yellow vertex until the “crease” passes through the upper vertex.
- Click on the yellow triangle to “crease”.
- Unfold the triangle completely.
- Drag each vertex of the triangle to the red point (the foot of the altitude).
- Click reset and experiment with different triangles.[list]