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Chapter 3: Polygons and Their Relations

# Area

Now we have talked about different kind of polygons. But we haven’t discussed the most important property of polygons-the area. Every polygon has area. Though sometimes we can’t see a polygon such as an atom, it still has area. An area is the number of square units in the region bounded by the polygons. Here are the formulas for calculating the most commonly seen polygons:

Rectangle: base x height

Square: side x side

Parallelogram: base x height

Triangle: (base x height)/2

Equilateral triangle: (side x side x Ö 3)/4

Kite: (diagonal 1 x diagonal 2)/2

Rhombus: (diagonal 1 x diagonal 2)/2

Heron’s Formula: If a, b, and c are the lengths of the sides of a triangle and s is the semiperimeter, such that s = ½(a+b+c), then area of triangle = Ö s(s-a)(s-b)(s-c).

Trapezoid: (base 1 + base 2)height/2

These are all the properties and concepts of polygons.  They should be firmly memorized because that you will see them so often on the tests.  Please take a few minutes break and click here to continue to the next chapter. (You can also click on the drop-down list below to jump to any chapter you like.)

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