perimeter = 4(3) = 12
area = 3^2 = 9- In rectangles and squares all angles are 90-degree angles.
It can’t be a square or a rectangle unless all angles are 90 degrees.
Let’s check out an example.
6.If the perimeter of a square is 28, what is the length of the diagonal of the square?
A) 2
B) 7
C) 7
D) 14Here’s How to Crack It
The perimeter of a square is 4s. So, 28 = 4s. Divide by 4 to find s = 7. The diagonal of a square divides
the square into two 45°-45°-90° triangles, with sides in the ratio of x:x: . If the side is 7, the diagonal is
7 . The answer is (B).
Polygons
Polygons are two-dimensional figures with three or more straight sides. Triangles and rectangles are both
polygons. So are figures with five, six, seven, eight, or any greater number of sides. The most important
fact to know about polygons is that any one of them can be divided into triangles. This means that you can
always determine the sum of the measures of the interior angles of any polygon.
For example, the sum of the interior angles of any four-sided polygon (called a quadrilateral) is 360
degrees. Why? Because any quadrilateral can be divided into two triangles, and a triangle contains 180
degrees. Look at the following example: