# Angle Relationships

The amount of space between two straight lines that have a common end point is called angle. Two angles can be related if certain conditions are met. Here, we will learn how to identify these kind of angles and use the correct term to describe them.

NameImageDescription
Vertical AnglesThe angles opposite each other when two lines cross. In the figure, the 1 and 3 are vertically opposite angles and they are always equals. Same goes for angles 2 and 4.
Corresponding AnglesThe angles in matching corners when two lines are crossed by another line, called the transversal. One is internal and the other external. They are equals if the two intersected lines by the transversal are parallel. In the figure, angles 1 and 2 are corresponding. The 1 is external and the 2 is internal.
Alternate Exterior AnglesAngles that are on opposite sides of the transversal of two other lines. Both are external. They are equals if the two intersected lines by the transversal are parallel. In the figure, angles 1 and 4 are alternate exterior angles.
Alternate Interior AnglesAngles that are on opposite sides of the transversal of two other lines. Both are internal. They are equals if the two intersected lines by the transversal are parallel. In the figure, angles 2 and 3 are alternate interior angles.
Adjacent AnglesTwo angles which share a common vertex and side, but have no common interior points. In the figure, the alpha and beta are adjacent angles.
Complementary AnglesTwo angles are called complementary when their sum is 90º. In the figure, the alpha and beta angles together form a right angle.
Supplementary AnglesTwo angles are called supplementary when their sum is 180º. In the figure, the alpha and beta angles together form a straight angle.

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