Cards | 10 |

Focus | Lines & Angles |

Topics | Acute & Obtuse Angles, Angles Around Lines & Points, Line Segment, Right Angle |

An acute angle measures less than 90°. An obtuse angle measures more than 90°.

Angles around a line add up to 180°. Angles around a point add up to 360°. When two lines intersect, adjacent angles are **supplementary** (they add up to 180°) and angles across from either other are **vertical** (they're equal).

A line segment is a portion of a line with a measurable length. The **midpoint** of a line segment is the point exactly halfway between the endpoints. The midpoint **bisects** (cuts in half) the line segment.

A right angle measures 90 degrees and is the intersection of two **perpendicular** lines. In diagrams, a right angle is indicated by a small box completing a square with the perpendicular lines.