Angle and Triangle Flash Cards You need 15 index cards for this!

Angle A B C

Two rays with a common endpoint called a vertex Two rays with a common endpoint called a vertex. Always name an angle with the vertex in the middle.

Adjacent Angles

Angles that share a vertex and a side.

Congruent Angles 64° 64° X Y

Angles with the same measure.

Vertical Angles

Angles formed by intersecting lines and are opposite each other Angles formed by intersecting lines and are opposite each other. Vertical angles are always congruent!

Acute Angles

The measure of the angle is less than 90°.

Obtuse Angles

The measure of the angle is greater than 90° and less than 180°.

Right Angles

The measure of the angle is 90°.

Complementary Angles

The sum of the two angles is 90°.

Supplementary Angles

The sum of the two angles is 180°.

SCALENE TRIANGLE

All three sides have different lengths:

ISOSCELES TRIANGLE

Has at least 2 congruent sides

EQUILATERAL TRIANGLE

All three sides are congruent

ACUTE TRIANGLE

All of the angles are acute (less than 90°)

OBTUSE TRIANGLE

One obtuse angle (greater than 90 less than 180)

RIGHT TRIANGLE

Has one right angle (90°)

Parallel Lines

Lines that are the same distance apart and never intersect (same slope)

Perpendicular Lines

Lines that intersect forming a perfect right angle

Transversal

A line that cuts across two or more other lines

Corresponding Angles

Angles that are in the same position

Interior Angles

Alternate Interior Angles are “across” from each other on the “inside”: (A and D) (B and C)

Exterior Angles

An angle that occurs outside of two lines when they are crossed by a transversal Alternate Exterior Angles are “across” from each other on the “outside”: (A and H) (B and G)