# What is an angle?

We are all familiar with the simplest geometricfigures: angle, square, triangle. Of course, we can explain in our own words what it is, but this is not enough to help the student, we need to know a clear definition. Here we will tell you what the angle is, and what they are. So, let's begin.

What is a point, it is clear to all. Euclid also gave her such a definition: "The point is that it has no parts." But, what is a straight line? This is a set of points constructed with the help of a ruler, it does not have a beginning and there is no end. If we put a point on a line at any place, we will have two rays having the same origin. The points are called large Latin letters: A, O, B ... The rays can be denoted by a small Latin letter (a, k, b) or two large letters (the first ray start, the second is any point on the ray: OA). Now we know which shape is called the angle.

Angle is a geometric figure that consists ofpoint and two outgoing rays. That is, if the point is denoted by O, and the rays OA and OB, we have an angle AOB. Their value is measured in degrees. This can be done with a protractor. The angle has two sides (rays OA and OB) and a vertex (point O). Be sure to remember, you can call the angle along the vertex (O) or three points (AOB or BOC), but the vertex letter should always be in the center. Now find out which are the corners.

## Types of angles

As it was written above, the angles are measured in degrees. Depending on the size of the angle, they are divided into the following types:

- Sharp corner. Has a value from 0 to 90 degrees.
- The angle is 90 degrees - straight.
- The obtuse angle is 90 and 180
- The unfolded corner. It is 180 degrees.
- If the angle is less than 360, but more than 180, such an angle is called nonconvex.
- The total angle is 360 degrees.

Angles not equal to 90 and 180 degrees are called oblique. If the angles are called equal, then they have the same value.

## Types of angles

Adjacent are the angles in which one sidegeneral, and the other two lie, not coinciding, on one straight line. The sum of such angles is 180 degrees. Simply put, if the developed angle is divided into two parts by a ray, we obtain adjacent angles.

The vertical angles are those thatThey are obtained at the intersection of two straight lines and no common sides. This definition may also sound different: angles, the sides of which are extensions of the sides of others, are called vertical. Such angles will always be equal in magnitude.

Now you know what angle is, and what they are.