Show students the angle found in the “Acute and Obtuse Angles” Notebook file. Ask them whether they think it is an acute or obtuse angle. Encourage individual students to provide definitions of each type of angle. Prompt them if necessary, pulling out the prepared definitions on the Notebook file. Establish with the whole class that the angle is obtuse. Ask: How could we prove this is an obtuse angle? Introduce the interactive protractor on the SMART Board!
Complete with a teacher's page PDF, an "Acute or Obtuse?" reproducible, and a launch-and-learn Notebook file, this mini-lesson helps to achieve the following learning objectives:
• Use a protractor to measure and draw angles.
This mini-lesson meets the following Common Core State Standards for Mathematics:4.MD.5: Recognize angles as geometric shapes that are formed wherever two rays share a common endpoint, and understand concepts of angle measurement.4.MD.6: Measure angles in whole-number degrees using a protractor.4.G.1: Draw points, lines, line segments, rays, angles (right, acute, obtuse), and perpendicular and parallel lines. Identify these in two-dimensional figures.This mini-lesson also meets the following NCTM Standards:• Understand such attributes as length, area, weight, volume, and size of angle and select the appropriate type of unit for measuring each attribute.• Select and apply appropriate standard units and tools to measure length, area, volume, weight, time, temperature, and the size of angles.