Question

Find the perimeter P of ▱JKLM with vertices J(2,2),K(5,3),L(5,−3),and M(2,−4). Round your answer to the nearest tenth, if necessary?

Answer 1

I get `18.3`.

Explanation:

Use the Pythagorean distance formula to get the length of each side. The distance between `(x_1,y_1)` and `(x_2,y_2)` is

`d=\sqrt{(x_1-x_2)^2+(y_1-y_2)^2}`

Put the numbers in and infer that

`|JK|=|LM|=\sqrt{10}`

`|KL|=|MJ|=6`

(Can you tell, why are two pairs of distances equal?)

Add these up to get the perimeter `=12+2\sqrt{10}`.

To get the square root term render `2\sqrt{10}=\sqrt{40}` and use the method given here to find that to the nearest tenth, `\sqrt{40}=6.3`. So the total perimeter is `12+6.3=18.3`.