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point

is an exact location in space

line

is a straight path of points that goes on and on in two directions

plane

is an endless flat surface

parallel lines

never intersects

intersecting lines

pass through the same point

perpendicular lines

are lines that form square corners

line segment

is a part of a line with two endpoints

ray

is a part of a line that has one endpoint and continues on forever in one direction

angle

is a figure formed by two reays that have the same endpoint. Angles are given special names depending upon their size.

right angle

an angle of 90°, as in a corner of a square or at the intersection of two perpendicular straight lines

acute angle

is open less than a right angle

obtuse angle

is open more than a right angle but less than a straight angle

straight angle

forms a straight line

degrees

angles are usually measure in this units

protractor

a tool that is used to measure and draw angles

polygon

is a closed plane figure made up of line segments. Each line segment is a side.

vertex

The point where two sides meet.

Equilateral Triangle

Has 3 equal sides

Isosceles Triangle

Has 2 equal sides

Scalene Triangle

0 equal sides

acute triangle

has three acute angles. All of its angles measure less than a right angle.

obtuse triangle

has one obtuse angel. One angle has a measure greater than right angle.