## 10.9 Chapter summary

- An arc is part of the circumference of a circle.
- To bisect means to divide into two equal parts.
- A perpendicular bisector is a line that intersects another line at right angles and divides the line into two equal parts.
- We measure angles in degrees (\(^{\circ}\)). We use a protractor to measure an angle.
- When the sum of two angles is equal to \(90^{\circ}\), we say that the two angles are complementary angles.
- When the sum of two angles is equal to \(180^{\circ}\), we say that the two angles are supplementary angles.
- The longest side of a triangle lies opposite the biggest angle of the triangle.
- The shortest side of a triangle lies opposite the smallest angle of the triangle.
- The sum of the lengths of the two shorter sides of the triangle must be greater than the length of the longest side of the triangle.
- A scalene triangle has three angles of different sizes.
- An isosceles triangle has two equal sides. It therefore also has two equal angles.
- An equilateral triangle has three equal sides and three equal angles. Each angle is equal to \(60^{\circ}\).
- The sum of the interior angles of a triangle is \(180^{\circ}\).
- The sum of the interior angles of a quadrilateral is \(360^{\circ}\).
- A square is a quadrilateral with all sides equal in length and all interior angles equal to \(90^{\circ}\).
- A rectangle is a quadrilateral with opposite sides equal in length and all interior angles equal to \(90^{\circ}\).
- A parallelogram is a quadrilateral with opposite sides equal and parallel.
- A rhombus is a quadrilateral with opposite sides parallel and all sides equal in length.