1.2.1 Using Formulas in Geometry (continued)

The lengths of the sides of this triangle are 10, x − 1, and 2 x − 7. To find the perimeter, simply add these three lengths and simplify. The formula for the area of a triangle is A = 1/2 bh , where b is the length of the base and h is the height of the triangle. The base b of a triangle can be any side of the triangle. The height h of a triangle is a segment from a vertex that forms a right angle with a line containing the base of the triangle. In the triangle given here, the base is represented by the expression x − 1 and the height is 10 units. So, to find the area of the triangle, multiply 1/2 by ( x − 1) and (2 x − 7), and then simplify.

Example 2 Crafts Application

To find the approximate amount of fabric used to make the 8 squares in the quilt, first find the amount of fabric needed for 1 square, which is equivalent to the area of 1 square. Once you have the area of 1 square, multiply that area by 8 to find the area of 8 squares. The total area of the 8 squares is the amount of fabric needed to make the 8 squares on the quilt.

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