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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.