Polygons

For ProProfs learning module

1. A polygon is a closed figure composed of three, four or more line segments that connect at their end points; there is no limit to the number of sides it can have. Each line segment is called the side The intersection at the endpoints is called the vertex The number of sides = the number of interior angles Polygons are named by the number of sides they have. Two common polygons are the triangle and quadrilateral . A triangle is a polygon having three sides and interior angles. A quadrilateral is a polygon having four sides and interior angles.

2. We can describe triangles two ways: by the nature of their sides and by the nature of their angles . Let’s first look at describing triangles by their angles . A triangle with three acute angles is called an acute triangle . A triangle with one obtuse angle and two acute angles is called an obtuse triangle . 0° < Angle < 90° 0° < Angle < 90° 90° < Angle < 180° 90° A triangle with one right angle and two acute angles is called a right triangle . The side opposite the right angle is called the hypotenuse . hypotenuse 0° < Angle < 90°

3. Next we will describe triangles by their sides . An isosceles triangle has sides with two equal lengths . An equilateral triangle has sides with three equal lengths . A scalene triangle has sides with three different lengths . 2” 2.82” 2” 3” 3” 3” 1.5” 2” 2.5”

4. A quadrilateral is a four sided polygon. Here are some common quadrilaterals. A rectangle is a quadrilateral where each set of opposite sides are equal in length and parallel to each other. All four interior angles are 90° . A square is just a special rectangle of four equal sides. A parallelogram is a quadrilateral where each set of opposite sides are equal in length and parallel (just like a rectangle ). The opposite interior angles are the same measure . Both rectangles and squares are special types of parallelograms. 2” 2” 4” 4” 90° 90° 90° 90° 3” 3” 1.4” 1.4” 45° 45° 135° 135° A trapezoid is a quadrilateral where only one pair of opposite sides are parallel. Top & bottom parallel, sides are not