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.

SUBJECTS: Maths YEARS: 3–4, 5–6 An angle is formed when two straight lines, or rays, meet at a point, called a vertex. Angles are measured in degrees. An angle can also describe an amount of turn.

Because if the triangle will have two obtuse angles (angles greater than 90°), then the sum of all three angles of the triangle will not be equal to 180°, it will be more than 180°. 4.