Course Guide - USAID Teacher Education Project

c) Angles can be categorized by measurement. When given pictures of acute, right,and obtuse angles, children intuitively know that they “look” different.Children may describe a right angle as a “square.” (Note that the symbol for a rightangle is a small square within the angle.) They may also say it looks “like a corner”since many of the “corners” they see (pages of a book, table, windows, etc.) are rightangles.Just as young children needed to “see” that any three-sided polygon regardless of itsorientation is a triangle, they now need to see that a right angle remains a right angle,even if its orientation is changed.d) When describing acute angles, children often call them “pointy,” especially if theyare less than 30°.e) Children usually lack ways to describe an obtuse angle, perhaps because theseangles are less obvious in their everyday environment. Teachers need to identify reallife examples of obtuse angles such as the hands of a clock at 10:10 or a stop sign.f) Having children discuss their ideas about angles in simple shapes such as patternblocks, can also help them differentiate among acute, right, and obtuse angles.g) Older children will be introduced to the idea of the 180° straight angle. This can bedifficult if students’ informal definition of an angle means that an angle “has acorner.”