A trio of triangle teasers
The ancient Greek geometer Euclid presented a list of five axioms he held to be self-evidently true. They are (or are equivalent to):
You can draw a line between any two points.
You can extend lines indefinitely.
You can draw a circle at any point with any radius.
All right angles are equal.
All triangles have internal angles that add up to 180 degrees.
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