# Angle

We explain what an angle is and how they are analyzed. Operations with angles and degrees. What types of angles exist?

### What is angle?

The angle is the **portion of the plane between two semi-lines with a common origin called a vertex** . In other cases, reference is made to the opening formed by two sides that start from that common point, or focus on the rotation of the plane with respect to its origin.

These concepts **correspond to geometry**, which is one of the branches of mathematics, but which find innumerable applications in many other fields, such as engineering, optics or astronomy. a. In all cases reference is made to a point in common, with two lines that start from that point and generate a certain opening, represented by an arc. The degree of opening of these arcs (and not their extension) is represented by the angle, no matter how far or near the vertex is made.

The concept of angle, then, refers to **a magnitude that can be analyzed and compared with others**, so there are operations between them. For that, the measurement of the angles is made in degrees, minutes, and seconds. The first (represented by the sign ) equals 60 of the second (represented by ), which in turn equals 60 of the third (represented by ).

**The number of degrees may amount to 360**, which is considered the complete turn. To give a daily example that exemplifies this, we can see the clock of needles: constantly the needles are forming angles. At 12 o'clock, when the two needles point exactly to the same side, the angle is 0 . At 3 it becomes 90, at 6 of 180, at 9 of 270, and at 12 o'clock again it will be 360, and it will return to start.

With regard to operations with angles, **we can add them together, subtract them from each other or multiply them and divide them** by whole numbers. If it is known that the angle is between two semi-lines, it can be said that a line can always be drawn that divides into two parts equal to the angle. That line is called the bisector, and any point on that equidist line on both sides of the angle.

See also: Trigonometry.

### Types of angles

There are many kinds of angles that can be given in the plane, some examples are indicated below:

**Null.**The null angle is the one that measures 0 °, the acute one is the one that measures between 0 ° and 90 °, the rectum the one that measures 90 °, the obtuse one that measures between 90 ° and 180 °, the concave one is the one that measures more 180 ° and the complete one is 360 °.**Supplementary.**The supplementary angle is the angle that is missing from an existing one to add 180 °, while the complementary angle is the one that is missing to add 90 °.**Adjacent**Two angles will be adjacent if they are consecutive with respect to a line, and will be opposed by the vertex if the sides are extensions of the sides of another angle.

More in: Types of angles.

Outside of these uses related to mathematics, **only two colloquial uses of the term can be mentioned** : on the one hand, we speak of angles to refer to the corners of objects. On the other hand, the term is used to refer to points of view, to the ways of seeing things from a person's vision.