# Point of triangle

1. Apr 5, 2004

OK I have right angled triangle, I no the lenght of the 3 sides. and the position
of two of the points but i wanna be able to figure where the 3rd point is. I
attached a rough sort of diagram so u no wot i'm talkin about. I 'm sure there
is enuf info there to find the point but i just can't get my head round it

Lenght of sides 13, 9 and SQROOT of 13^2 + 9^2 = 16(roughly)
Points = Bottom -> (273,541)
Top -> (273,525)

Last edited by a moderator: May 1, 2017
2. Apr 5, 2004

### chroot

Staff Emeritus
Do you know how to decompose vectors into components?

- Warren

3. Apr 5, 2004

I dunno wot that is??
Could u explain???

4. Apr 5, 2004

### chroot

Staff Emeritus
A vector is a directed line segment -- a distance and a direction.

The components of a vector $\vec u$ on a plane are $(l \cos \theta, l \sin \theta)$ where $l$ is the magnitude of the vector.

If you don't know how to use vectors, I'm afraid I won't have much luck helping you understand how to solve this problem. I can't think of an easier way to do it, but I'm a little tired right now.

- Warren

5. Apr 5, 2004

Ok thats sound no i don't understand vectors. I'm actually programming it so i mite be able to work another way around it

6. Apr 5, 2004

Your model still allows for two possible points. If only two of the points are fixed, then the third can be as you showed in the diagram or it could be reflected across the line described by the two points.

That being said, you could probably figure it out using slopes. Describe the slopes in terms of the points and stipulate that the slopes satisfy the equation m1m2 = -1.

7. Apr 5, 2004

I was thinkin i could work it out by gettibg the area and then workin backwards to the answer but i will still have two unknowns so i don't think that will work properlt

8. Apr 5, 2004

Two unknowns? You're going to get two solutions, but you should have only a single unknown.

9. Apr 5, 2004

### chroot

Staff Emeritus
Well, I really do only see two ways to do this: vector geometry or plain ol' line-equation algebra.

If you have only this one problem to solve, we can give you the solution -- but if you need to write code to solve any triangle like this, you're gonna need to bone up on some math. It's pretty tough to write code to do something you don't know how to do by hand.

- Warren

10. Apr 5, 2004

Two solutions thats what i meant, same as.

11. Apr 5, 2004