Saturday, December 1, 2012
Thursday, November 22, 2012
AREA
Area of a SquareThe area of a square that has a side-length of 1 cm is 1 square centimetre (or 1 cm2). To find the area of a square by the method of counting squares, we divide the square into smaller squares of one centimetre side-length . Consider a square that has a side-length of 4 cm. Using the method of counting squares, we find that the area of the square is 16 cm2. Clearly, the square contains 4 rows of 4 squares. Therefore:
The area of a square is equal to its side-length multiplied by its side-length. That is: | |
To find the area of a region enclosed within a plane figure, draw a diagram and write an appropriate formula. Then substitute the given values and use a calculator, if necessary, to obtain the required area. | |
| Perimeter |
| A square and an equilateral triangle are both examples of regular polygons. Another method for finding the perimeter of a regular polygon is to multiply the number of sides by the length of one side. Let's revisit Examples 3 and 4 using this second method. | ||
| Example 3: | Find the perimeter of a square with each side measuring 2 inches. | |
| Solution: | This regular polygon has 4 sides, each with a length of 2 inches. Thus we get: | |
| Example 4: | Find the perimeter of an equilateral triangle with each side measuring 4 centimeters. | |
| Solution: | This regular polygon has 3 sides, each with a length of 4 centimeters. Thus we get: | |
| Example 5: | Find the perimeter of a regular pentagon with each side measuring 3 inches. | |
| Solution: | ||
| Example 6: | The perimeter of a regular hexagon is 18 centimeters. How long is one side? | |
| Solution: | ||
| Let | ||
| Summary: | To find the perimeter of a polygon, take the sum of the length of each side. The formula for perimeter of a rectangle is: | |
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