An acute angle is one whose measure is less than 90 degrees. It is one of three kinds of angles that are typically talked about in geometry classes. I will discuss each so that you can remember the differences between them.

The three kinds of angles are acute, right, and obtuse angles. As I said before, an acute angle has a measure of less than 90 degrees. A right angle has a measure of exactly 90 degrees. That is like the angles of a square or a rectangle. An obtuse angle has a measure of more than 90 degrees.

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When two rays AO and BO meet at a common point (or OA and OB start drom a common point O), then there are two angles AOB at O: Smaller angle AOB (or BOA) and larger angle AOB( or BOA) at O.

An angle is the measure of the inclination of two rays with a common point both rays..

The angle between the opposite rays is 180 degrees or pi radians, or 2right angles.

If a ray stands on another ray , then there are two angles adding to two right angles(or 180 degrees , or pi radians).

A ray is said to make right angles when it stands on another ray if the the two angles it makes on the other ray are equal in measure.

If the measure of angle between the two rays meeting at a common point or starting from a common point is less than the right angle (90 degrees, or pi/2 radians), then the angle is said to be acute.