Course Guide - USAID Teacher Education Project

g) Note that certain polygons include these specific angles. For example, anequilateral triangle has three 60° angles for a total of 180°. A square, with four 90°angles, has an interior angle sum of 360°. If a square is cut on the diagonal, it willhave one 90° angle and two 45° angles. (Again, each of the resulting two triangleshas an angle sum of 180° degrees.)h) Other benchmark angles devolved from the 90° angle can be used for comparingangles and estimating their measurement. For example, if one knows how to create a45° angle, one can determine if a given angle is greater or less than 45°. The samewould be true for an angle that looks to be between 90° and 135°.2. How do children think about these concepts?a) One of the most important considerations when trying to establish similaritybetween two figures is their corresponding sides. This is relatively easy if the figureshave the same orientation as in this diagram (which also allows for establishing thelength of other sides based on the 3:12 ratio of the vertical side):