# GeoBasics2.2 part 2

- Author:
- Mark Brouwer

## GeoBasics2.2: I can prove that the interior angles of a triangle sum to two, right angles

Proving Interior Angles of a Triangle, part 2

## 1. The Interior Angles of a Triangle

Select the statement that best represents the conclusion of the proof

## 2. The crucial premise

In order to prove the conclusion, you must first find three angles that sum to 180° because they are three adjacent angles on a straight line. Then you must connect each of these angles to the interior angles of the triangle. Select the crucial premises that allow you to connect each of the angles of the triangle to three angles that sum to 180°

## 3. The Proof

Using only the points and lines given in the figure above, prove that the interior angles of HAN sum to two right angles