An acute angle is less than 90°. An obtuse angle is between 90° and 180°. A reflex angle is between 180° and 360°. The size of an angle can be estimated without using a protractor.

What you need: ruler, protractor, pencil and paper. Use these to construct a triangle when you know the length of 1 side and the 2 angles at each end of it. In this case use the length 8 cm, and the ...