# 10 Facts about Angles

If you want to know one of the important topics in mathematics, you have to check out **Facts about Angles**. The figure formed by two rays in planar geometry is called an angle. The vertex of the angle shares the common endpoint. Find out more facts about angles below:

## Facts about Angles 1: the word angle

The word angle is taken from the Latin word of angulus. It means corner. There is no angus in Latin word for it is the primitive form. Therefore, angulus is a diminutive.

### Facts about Angles 2: Eudemus

Eudemus thought that an angle was a deviation from a straight line. Proclus had his own opinion about angle. He believed that an angle could be a relationship, a quantity or a quality.

## Facts about Angles 3: Carpus of Antioch

Carpus of Antioch believed that an angle was the space or interval between intersecting lines.

### Facts about Angles 4: the mathematical expression

It is very common for us to use the Greek letters when we want to pick the variables of size of angle. The word p is not used in this mathematical expression for it can trigger the confusion.

## Facts about Angles 5: acute angles

You can call it acute angle if the angles are smaller than a right angle. It means that it is less than 90 degree. The word ‘acute’ means sharp. Check **facts about absolute value** here.

### Facts about Angles 6: a right angle

Now let’s define the right angle. You can call it a right angle if the angle is equal to ¼ turn. The two lines used to make the right angle should be perpendicular, orthogonal or normal.

## Facts about Angles 7: the obtuse

The word obtuse means blunt. This obtuse angle is defined if the angles are between 90 degree and 180 degree. These angles are smaller than a straight angle and larger than a right angle.

### Facts about Angles 8: reflex angle

Can you define the reflex angle? It has the angle between 180 degree and 360 degree. The angles are less than 1 turn and larger than a straight angle.

## Facts about Angles 9: a straight angle

Define the straight as an angle which is equal with 180 degree or ½ turn. Get **facts about algebra** here.

### Facts about Angles 10: a perigon

A perigon is also called a complete angle, or a full angle. It has 360 degree or a complete 1 turn.

What do you think on **facts about angles**?