Interior Angles of a Triangle

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The interior angles of a triangle always add up to 180° (or radians). You can see that by putting the corners together and observing the straight line that they create.
Contributed by: Jon McLoone (March 2011)
Open content licensed under CC BY-NC-SA
Snapshots
Details
Drag the corners of the triangle to change the angles but notice how the total of the angles never changes.
Permanent Citation
"Interior Angles of a Triangle"
http://demonstrations.wolfram.com/InteriorAnglesOfATriangle/
Wolfram Demonstrations Project
Published: March 7 2011