Course Guide - USAID Teacher Education Project

Finally, ask students to name a real life example for each of these three types ofangles.Ensure that students understand the vocabulary required for the rest of the lesson,including "line segments," "rays," and "vertex."b) Have students draw two squares of different sizes, then ask which square has thebigger angles. Students may be puzzled by this question, and may ask what you meanby "bigger." Ask what they think and to predict what a child would think. Afterhearing their answers, ask why a child may think that the angles in the larger squareare bigger than the ones in the smaller square.Ask students why the angles in both squares are the same even though the size of thesquares is different.Draw two similar triangles on the board and ask the same questions.Finally, draw two "branching" angles whose angle measurements are the same buthave different length rays emanating from the vertex. Ask if these angles are thesame. As the discussion develops, elicit from students that angles are the spacebetween two rays or line segments but that the length of the line segments or rays donot determine the size of the angle.c) After students understand that the size of an angle is not determined by the lengthof the rays or line segments, ask how they would determine if one angle is "bigger"than another.Draw two acute angles of different sizes and ask which is the "bigger" angle, andwhy.Draw a right angle, then an obtuse angle and ask the same question.Notice how students describe their perceptions.If the angles look different, how can we quantify their size, and what sort ofmeasurement system should be used? If students mention degrees, remind them ofthe benchmark angles they worked with in the prior session.Many will know the terms "acute," "right," and "obtuse" and the angle measurementsof less than 90°, exactly 90°, and between 90° and 180°.When describing an obtuse angle, students may say that it is "greater than 90°. Tochallenge this, draw a straight line with a point (vertex) on it and ask them what sortof angle they see.To demonstrate, draw two clock faces on the board and set one to show 3 o'clock.Ask what angle the hands make. Draw 6 o'clock on the second clock and ask whatsize angle the hands make.Clarify that this is called a straight angle, and its measure is 180°. Ask through howmany degrees the hour hand will have gone by 9 o'clock. Note that angles greater