geometry
posted by Millwe on .
On a graph, the points (4,2),(7,2),(9,5) and (2,5) are connected in order to form a trapezoid. To the nearest tenth, what is its perimeter?

Compute the four side lenghts using the pairs of coordinates.
The side that goes from (4,2) to (7,2) has a length of sqrt[(74)^2 + (2 (2)^2] = 5
Do the others the same way.
Then add all four. 
Thank you for your help, I still don't understand

In order to figure the length of a line segment, you have to rely on the Pythagorean Theorem. If that doesn't sound familiar, you need to review your text. The theorem states that in a right triangle with legs a and b, with hypotenuse c,
c^{2} = a^{2} + b^{2}
Now, if you plot two points on a piece of graph paper, such as (7,2) and (9,5), the line joining the points will be a slanting line. If you draw horizontal and vertical lines from each point, they will intersect to form a right triangle. The length of the legs are just the xdistance from 7 to 9 = 2, and the ydistance from 5 to 2 = 3.
So, the length of the hypotenuse is given by
h^{2} = 2^{2} + 3^{2}
h^{2} = 13
so,
h = √13
If you follow these steps for each side of the figure, you can add up all the lengths to get the perimeter.