Why does the interior angle measures of a triangle equal 180 degrees?

Why do the angles in a triangle add up to 180°??

Proof of the Sum of Angles of a Triangle Measure 180 Degrees | Don't Memorise

Proof: Sum of measures of angles in a triangle are 180 | Geometry | Khan Academy

The Sum of the Interior Angles in a Triangle are 180° Demonstration

How YOU Prove the Angles of a Triangle Equal 180 Degrees | 8.G.A.5 💗

Special Triangles and Reference Angles

Angles in a Triangle Add Up to 180 Degrees - Video

Finding the Missing Angle of a Triangle: A Step-by-Step Guide | Triangles | Math with Mr. J

11+ Guides: Proving That Angles In Triangles ALWAYS Total 180°

Angles of Triangle: Sum of Interior Angles and Exterior Angle Theorem by @MathTeacherGon

Exterior Angle Theorem For Triangles, Practice Problems - Geometry

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Math Antics - Triangles

Angles in a triangle add up to 180 degrees - exercises and proof

Why do exterior angles of any polygon add up to 360°?

If two angles of a triangle are equal, the sides opposite to them are also equal.

Equal Angles Opposite Equal Sides

To Verify that the sum of all interior Angles of a triangle is 180 degree. Cutting Pasting Activity

Sum of interior angles of a triangle is 180°