Area And Perimeter

Area and Perimeter Triangles A triangle is the figure defined by three segments that connect three noncollinear points. The segments are called the sides and the points are the vertices of the triangle. There are four special types of triangles: An acute triangle has all angles less than 90 , an obtuse triangle has one angle greater than 90 , a right triangle has one angle equal to 90 , and an equilateral triangle has three equal sides (and three equal angles, 60 ). b h

Area of a triangle 1 A . b. h 2

10. in 7.5. in 1. . A bh 2 Area: b h

2

A = 37.5 in In order to find the perimeter you must know a bit more about the triangle. If you are working with a right triangle, you only need to know the lengths of two sides (or one side and one of the acute angles) to find the area and perimeter.

3. cm 4. cm 1. . A ab 2 a b

2

A = 6 cm All equilateral triangles are similar (they are the same shape but not necessarily the same size). If you know the length of one side of the triangle, you can calculate its area and perimeter a 3. cm Area: 2

A

a . 3 4 2

A = 3.897 cm Find the area, perimeter and height (as shown) of a triangle given the lengths of the sides, a, b, and c.

a 17. in b 35. in c 25. in Use Heron's formula to find the area: Semiperimeter: 1. s a b c 2 Area:

A

s. s

a . s 2

b . s

c

A = 0.128 m Perimeter: P a b c P = 1.956 m Height: We'll use a solve block. Guess values: h 10. in x 20. in