|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.