Points, Lines, Planes & Angles

Complementary angles:

Two angles that add up to 90°

Supplementary angles:

two angles whose measures add up to 180 degrees.

Angles on a straight line:

are angles that form a linear pair and add up to 180 degrees.

Vertical angles

are angles that are opposite each other when two lines intersect, and they are always equal in measure.

Angles around a point:

are formed by two rays with a common endpoint, and their measures add up to 360 degrees.

Angles inside a triangle

The three angles inside a triangle. They always add up to 180°

Bisector:

divides an angle into two equal angles.

Midpoint:

divides a segment into two equal lengths.

perpendicular

are two lines that meet at a 90° angle (a right angle).

line

A straight path that goes on forever in both directions.

Segment:

A part of a line with two endpoints.

Ray:

A part of a line that starts at one endpoint and goes on forever in one direction.

Concurrent lines:

Three or more lines that meet at the same point.

Parallel lines:

Lines in the same plane that never meet

Transversal:

A line that crosses two or more lines at different points.

Transversal:

A line that crosses two or more lines at different points.

Perpendicular bisector:

A line that cuts a segment into two equal parts at a 90° angle.

Projection of a point onto a line:

The closest point on the line to the given point.

Projection of a segment onto a line:

The shadow of a segment on a line, made by drawing perpendicular lines from its endpoints.