Question

The coordinates of the vertices of a triangle are (−4,2), (5−1), and (−3,−2).

What is the perimeter of the triangle, to the nearest tenth of a unit?

A: 13.1 units

B: 19.6 units

C: 21.7 units

D: 38.2 units

Answer 1

Find the distances between every pair of vertices using the distance formula:

d = √[(x2 - x1)^2 + (y2 - y1)^2]

1) d = √[(5+4)^2 + (2+1)^2] = √[81 + 9] = √90

2) d = √[(1)^2 + 4^2] = √[1 + 16] = √17

3) d = √[8^2 + 1^2] = √[64 + 1] = √65

Perimeter = √90 + √17 + √65 = 21.7