Khan Academy: Angles in a Triangle Sum to 180 Degree Proof

How can learners use algebra to solve a geometry problem? Help learners create an equation that shows the relationship between the number of sides of a polygon and the sum of the interior angles. Students are asked to divide the...

An informative lesson contains a brief explanation of how the sum of the angles of a triangle is a line. The lesson continues with determining the missing angle in a triangle, or solving for a variable. Using the sum of the...

Your visual geometry learners will appreciate triangle drawings as they model the triangle sum theorem and algebraically solve to find the missing interior angle in a triangle. Practice problems increase in complexity and vary in their...

The measures all add up. The presentation, part of a helpful playlist on geometry, provides the statement of the Triangle Sum Theorem. Using the theorem, the video shows how to find the missing measure of an angle.

Are you working on finding the missing angles of triangles in your class? Consider this video. An instructor uses the triangle sum theorem to create an equation that helps her find the missing angles. She explains each step and writes...

Are you working on finding the missing angles in triangles in your class? Consider this video. An instructor uses the triangle sum theorem to create an equation that helps her find the missing angles. She explains each step and writes...

The interior angles of any and ALL triangles adds up to 180 degrees. So if given two of the angle degrees, is it possible to find the value of the third angle? Yes! Use the triangle sum theorem to solve for the missing angle. Watch this...

Use the Triangle Sum Theorem to find the value of each of the inside angles of a triangle. This triangle problem has to do with the ratio of the angles to each other. Find the measure of each angle if the ratio is 1:3:8. Not sure how to...

Learn how to identify an equilateral triangle by evaluating its congruent sides. Once you've determined that that sides are congruent you'll be able to use the triangle sum theorem to determine the angles in an equilateral triangle. This...

If you add the value of the three interior angles in a triangle will it equal 180 degrees? Yes it will. The instructor illustrates and proves the Triangle Sum Theorem. Follow closely as she explains her proof.