The flat angle is, in terms of geometry, the space between an intersection between two lines whose **opening measures 180 degrees** or 180º. Since the angle is 180º there is no difference between two lines or a line and we can say that **the angles in a straight line always add up to 180º**.

The main characteristic of the flat angles is that when it changes direction it will always be the opposite. We can associate it with the popular expression **‘180 degree turn’** when a person completely changes his opinion for the opposite direction for example: “Last week he defended the rights of immigrants and now wants to create a law to get them out of the country, he gave a 180º turn in his speech! ”

If we take a circle, which measures 360º, we can say that half of the circle is 180º or a flat angle. And half of a flat angle is 90º or a right angle.

The angles can be measured with a **conveyor**. The most common conveyors are precisely 180º, that is, they complete a flat angle.

It is believed that the **origin of the 360º** for a complete circle comes from ancient calendars, such as that of the Persians and that of the Egyptians, who already had 360 days per year. The ancients observed in the stars that revolve around the polar star, that they move one degree per day until a full circle is drawn in 360 days.