Angles greater than 0° , but less than 90° are called acute angles.
Angles greater than 90° , but less than 180° are called obtuse angles.
Angles equal to 90° are right angles.
Angles greater than 180° , but less that 360° are called reflex angles.
Two adjacent angles that add up to 90° are called complementary angles.
Two adjacent angles that add up to 180° are called supplementary angles.
Multiple angles on a line always add up to 180° .
Multiple angles at a point always add up to 360° .
Parallel Lines
Lines are parallel if..
Alternate Interior angles are equal. (Z-rule)
Corresponding angles are equal. (F-rule)
Co-Interior angles are supplementary. (C-rule)
Vertically Opposite angles are equal. (X-rule)
Midpoint
The midpoint of a line segment is the point that is halfway between the endpoints of the line segment.
Median
The median of a triangle is the segment from a vertex to the midpoint of the opposite side.
Altitude
The altitude of a triangle is a line segment from one vertex of a triangle to the opposite side so that the line segment is perpendicular to the side.
Angle Bisector
The angle bisector is a line that divides an angle into two parts.
Perpendicular Bisector
The perpendicular bisector is a line which cuts a line segment into two parts at 90°.
