Label angles as right, obtuse or acute. Optionally estimate or use a protractor to measure the actual angles.
These worksheets require students to look at an angle and identify whether it is right, acute or obtuse. The worksheets start out with the base leg of the angle always laying horizontal, which is the easiest way to visualize whether the angle is acute or obtuse. Earlier worksheets also avoid angles that aren't quite right angles (unless the angle really IS a right angle) to make the acute/obtuse determination more obvious. Subsequent worksheets have the base angle rotated slightly which requires more spatial thinking, and the final set of worksheets has angles that are near right angles and may require a protractor to determine if their are acute or obtuse.
Each angles worksheet in this section also provide great practice for measuring angles with a protractor. The actual angle is provided on the answer key, so in addition to identifying whether an angle is obtuse or acute, you can suggest that students mesaure the angle with a protractor and supply the measurement as part of their work.