The Math Forum

Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Math Forum » Discussions » Math Topics » geometry.pre-college

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: finding third coordinate
Replies: 3   Last Post: Jun 11, 2009 9:21 AM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
Greg Pack

Posts: 1
Registered: 6/11/09
Re: finding third coordinate
Posted: Jun 11, 2009 9:21 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

Connect the points of the coordinates you are given and you have a segment
that is either a hypotenuse or a leg of your right triangle. Now all you
need is a third point. Easy. You can choose any point from one of three
infinite sets of possibilities. One set is a circle and the other two are

Suppose your segment is a hypotenuse. Find the midpoint and use it as the
center of a circle through the endpoints. Every point on this circle can be
the vertex of the right angle of your right triangle. Pick any point on the
circle [except the endpoints]. There are an infinite number of third points
you can use to find the coordinates. Use the standard equation of a circle
with your mid-point center (h, k) and a radius half the length of your
segment to show an equation for your locus of points.

Suppose your segment is a leg. Find the slope of your segment. Use the
opposite of the slope's reciprocal to give you the slope of a line
perpendicular to your leg. Now use the point-slope form of a linear
equation to find the equation of the line through each endpoint of your
[segment] leg. This line represents an infinite number of points that would
work as your third point to form a right triangle. Repeat the process and
you have another equation for another infinite set of possible third points.

Hope that helps.

----- Original Message -----
From: "koolelectrical" <>
To: <>;
Sent: Tuesday, June 09, 2009 6:43 AM
Subject: finding third coordinate

>I wanna know that how can i find third coordinate of right angled
> triangle when i know two coordinates?

Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© The Math Forum at NCTM 1994-2018. All Rights Reserved.