Mathematics » Math Models and Geometry I » Use Properties of Rectangles, Triangles, and Trapezoids

# Key Concepts

## Key Concepts

• Properties of Rectangles
• Rectangles have four sides and four right (90°) angles.
• The lengths of opposite sides are equal.
• The perimeter, $$P$$, of a rectangle is the sum of twice the length and twice the width.
• $$P=2L+2W$$
• The area, $$A$$, of a rectangle is the length times the width.
• $$A=L\cdot W$$
• Triangle Properties
• For any triangle $$\Delta ABC$$, the sum of the measures of the angles is 180°.
• $$m\angle A+m\angle B+m\angle C=180°$$
• The perimeter of a triangle is the sum of the lengths of the sides.
• $$P=a+b+c$$
• The area of a triangle is one-half the base, b, times the height, h.
• $$A=\frac{1}{2}bh$$

## Glossary

### area

The area is a measure of the surface covered by a figure.

### equilateral triangle

A triangle with all three sides of equal length is called an equilateral triangle.

### isosceles triangle

A triangle with two sides of equal length is called an isosceles triangle.

### perimeter

The perimeter is a measure of the distance around a figure.

### rectangle

A rectangle is a geometric figure that has four sides and four right angles.

### trapezoid

A trapezoid is four-sided figure, a quadrilateral, with two sides that are parallel and two sides that are not.