Plane geometry deals with the properties of figures, that lie in one plane. The word geometry comes from the Greek and means "land measurement"., Without them, our houses would be uneven, our walls would be crooked, and we couldn't find our way across the sea.
Let's start with the point. It indicates a spot in space. He has no length, width, height or depth.
One point, who moves, creates a line. There are different types of lines:
A horizontal line is horizontal, like the surface of calm water.
A vertical line runs from top to bottom and is perpendicular or perpendicular to a horizontal line.
A slanted line is neither horizontal nor vertical.
When a line steadily changes direction, is called a curve.
The direction always stays the same, her name is Straight. Parallel lines are straight, which, if they are in one plane, never touch, as long as you make them.
Angles are formed by two straight lines, emanating from the same point. The two lines are the sides of the angle. The point, where both legs meet, is called the vertex of the angle.
A quarter of a circle forms a right angle. He's ¼ of 360 City (written 360°), also 90°.
Any angle is called an acute angle, which is less than a right angle or less than 90°.
An obtuse angle is greater than 90°, but less than 180°. A line, moving sideways, creates a surface. It has length and breadth, but no height or depth. A flat surface, like a tabletop, is called a level.