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Geometry Basics

Welcome to the Geometry Basics website!

By connecting two points with a straight path you get a line segment.
A line segment is the shortest possible path between two points.
This picture demonstrates that a curved path is not the shortest path, which is why a line can't be curved.
If the line was curved it would not be the shortest path, therefore a line can not be curved.
This picture shows that a line continues forever in both directions.
A line is the same as a line segment, but it goes on forever in both directions.

You put arrows at the ends of a line to show that it doesn’t stop in either direction.
Shows half of a line.
A ray is the same as a line, but it only goes on forever in one direction.
picture showing that an angle is the space between two connecting lines.
An angle is the space between two connecting lines. The size of an angle is measured in degrees.
The previous angle shown measures roughly 45 degrees.

You can think of the measure of an angle as the amount that you would need to rotate one of the lines to get to the other.

A full rotation measures 360 degrees.


Since 45 degrees is 1/8th of 360 degrees, the angle shown is 1/8th of a full rotation.
Picture of an angle that measures 90 degress.
A right angle is an angle that measures exactly 90 degrees. A right angle is 1/4th of a rotation.

The corners of a paper are right angles!
Picture of an angle less than a 1/4th of a rotation.
An acute angle is any angle less than 90 degrees.

Things that are small are cute, acute angles are smaller than right angles.
Picture of an angle larger than 1/4th of a rotation.
An obtuse angle is any angle larger than 90 degrees. “Obtuse” is kind of a big word, an obtuse angle is any angle bigger than a right angle.
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