Encyclopedia>Geometry>Planar Figures>Triangles>Triangle Attributes>What Is the Sum of Angles of a Triangle?

You know that a triangle is a geometric figure with three sides (edges) and three corners (angles). That’s how it got its name! If you use a protractor and measure all the angles in a triangle, you will find that the sum of the angles is always equal to $180$°.

Rule

The sum of all three angles in a triangle is always $180$°.

There are four types of triangles: equilateral triangles, isosceles triangles, right triangles and all other triangles that can’t be categorized in any of the previous three ways— we call these types of triangles scalene triangles. These types of triangles have three different angles and therefore, also three different side lengths.

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