Random co-ordinates question

1. Nov 29, 2005

lektor

Hey can someone tell me how to find the co-ordinates on this diagram.

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2. Nov 30, 2005

HallsofIvy

Actually, no, because there is no coordinate system!

Do you intend to have a coordinate system with x and y axes horizontal and vertical?

Assuming that and that you are given coordinates (x,y) and (x2,y2) you can find the slope and equation of the line between them but you would still need to know the radius of the inner circle to find the coordinates of the point marked with a "?".

3. Nov 30, 2005

BobG

Without a reference frame, you can't find the coordinates. However, you can find the coordinates relative to X2,Y2 and X,Y.
If you let X2,Y2 be your origin, you can define your principal direction as being directed towards X,Y. Whether you create a unit vector in this direction or use some other length vector in this direction to define your reference, ? will just be some scalar multiple of your reference vector.
In other words, you can set it up so that if the value of X, Y, X2, Y2, and Z were later given, the coordinates of ? would naturally follow.

Last edited: Nov 30, 2005
4. Nov 30, 2005

lektor

Hey in reply to the first post Z is the radius of the inner circle, and this was for a friend who is trying to make a program to simulate the tides.