# Find the other end of the diameter

• Nov 15th 2009, 03:40 AM
jasonlewiz
Find the other end of the diameter
A circle with the center at (5,1) has a diameter that terminates at (6,3) . Find the other end of the diameter.

This is the formula of finding the center of two point

x=1/2(x1+x2)
y=1/2(y1+y2)

but what if the center is given and you have to find the other end,.,what is the formula?
• Nov 15th 2009, 04:46 AM
earboth
Quote:

Originally Posted by jasonlewiz
A circle with the center at (5,1) has a diameter that terminates at (6,3) . Find the other end of the diameter.

This is the formula of finding the center of two point

x=1/2(x1+x2)
y=1/2(y1+y2)

but what if the center is given and you have to find the other end,.,what is the formula?

1. Let $C(x_C, y_C)$ the midpoint of a line segment (in your case it is a diameter). Then your formula becomes:

$\begin{array}{l}x_C=\frac12(x_1+x_2) \\y_C=\frac12(y_1+y_2)\end{array}$

2. You must know the coordinates of 2 points to calculate the coordinates of the third one. For instance: If you know the coordinates of the midpoint and the coordinates of $P(x_1, y_1)$ then you have to solve the equations for $x_2$ respectively for $y_2$
• Nov 15th 2009, 04:55 AM
ukorov
-deleted post-
• Nov 15th 2009, 05:06 AM
ukorov
Quote:

Originally Posted by jasonlewiz
A circle with the center at (5,1) has a diameter that terminates at (6,3) . Find the other end of the diameter.

This is the formula of finding the center of two point

x=1/2(x1+x2)
y=1/2(y1+y2)

but what if the center is given and you have to find the other end,.,what is the formula?

for x coordinate of the other end:
$5 = \frac{x + 6}{2}$
for y-coordinate of the other end:
$1 = \frac{y + 3}{2}$
• Nov 15th 2009, 08:09 AM
Soroban
Hello, jasonlewiz!

Quote:

A circle with the center at C(5,1) has a diameter that terminates at A(6,3).
Find the other end of the diameter.

Did you make a sketch? . . . The answer will be obvious.

Code:

      |              A       |              o       |              ↑       |              ↑2       |        C    ↑       |  + ← ← o → → +       |  ↓        1     --+---↓-----+----------       |  ↓    5       |  o       |  B

To get from the center $C(5,1)$ to point $A(6,3)$,
. . we move 1 unit right and 2 units up.

Hence, to get the other end of the diameter $B$,
. . we start at $C$ and move 1 unit left and 2 units down.

Got it?