# Thread: perimeter of a triangle

1. ## perimeter of a triangle

Could someone please help me figure out where to start to get the answer to this?

2. Originally Posted by sanee66
Could someone please help me figure out where to start to get the answer to this?
use the distance formula to find the length of the sides. then just add them together.

recall, the distance formula, that is, in this case, the formula for the length of a line is:

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

do you think you can continue now?

3. ## perimeter of a triangle

I come up with 232. Would this be right?

4. Originally Posted by sanee66
I come up with 232. Would this be right?
hmmm. i got 25.502. i'm not sure how you managed to get that.

triangle DEF has three sides: DE, EF and DF.

we have: $D(-4,6) \mbox { , } E(5,3) \mbox { , } F(3,-2)$

So, the length of DE is:

$DE = \sqrt {(5 - (-4))^2 + (3 - 6)^2} = \sqrt {90}$

the length of EF is:

$EF = \sqrt {(3 - 5)^2 + (-2 - 3)^2} = \sqrt {29}$

the length of DF is:

$DF = \sqrt {(3 - (-4))^2 + (-2 - 6)^2} = \sqrt {113}$

The perimeter is the length of all the sides, therefore

Perimeter $= \sqrt {90} + \sqrt {29} + \sqrt {113} \approx 25.502$

5. ## perimeter of a triangle

i was weird and took x1-x2 and y1-y2 instead of the other way around. Thanks for all your help.

6. Originally Posted by sanee66
i was weird and took x1-x2 and y1-y2 instead of the other way around. Thanks for all your help.
It makes no difference.
Since you are squaring
$(y_1-y_2)^2 = (y_2-y_1)^2$