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Geometry flash cards for my math class. (In my examples, this sign: < is supposed to be an angle sign)

Supplementary angles

Two angles whose sum is 180 degrees.
EX: <ACB + <BCD = 60 + 120 = 180 degrees.

Complementary angles

Two angles whose sum is 90 degrees.

Acute angle

An angle less than 90 degrees but more than 0 degrees.


An exact location in space.

Obtuse angle

An angle whose measure is greater than 90 degrees, but less than 180 degrees.


A straight path that extends without end in opposite directions.

Right angle

An angle that measures 90 degrees.


(mathematics) a straight line extending from a point


(mathematics) an unbounded two-dimensional shape

Vertical angles

a pair of opposite congruent angles formed by intersecting lines

Parallel lines

coplanar lines that do not intersect

Perpendicular lines

Two lines that intersect to form right angles

Acute Triangle

a triangle whose interior angles are all acute

Obtuse Triangle

a triangle with one obtuse angle

Equilateral triangle

a triangle with three congruent sides

Isosceles triangle

a triangle with two congruent sides

Scalene triangle

a triangle with no two sides of equal length

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