The acute angle is the space between two lines that share the same vertex whose inclination or **opening is greater than 0 degrees (0°) and less than 90 degrees (90°)** .

In geometry, it is important to know how to identify acute angles since being visually less than 90° (a quarter of a circle), it makes easier an approximate visual identification of the type of angles within a triangle or within a plane.

Acute angles can be found, for example, in equilateral triangles since they are characterized precisely by being composed of three acute angles, that is, three angles of less than 60°.

In trigonometry, a science that studies the relationship of the elements of a right triangle, acute angles can be identified taking into account:

- The sum of the interior angles of a triangle total 180°,
- the right triangle is composed of an angle of 90° so the other two angles must add 90° ( complementary angles),
- If two angles add up to 90°, then both are acute angles.

## Types of angles

The types of basic angles for the knowledge of geometry and trigonometry are the following:

**Acute angle**: angles measuring less than 90°.**Obtuse angle**: angles measuring more than 90°.**Right**angle: angle measuring 90°.**Plain**angle: angle that measures 180°.