# Anyone know how to use Graphmatica?

Discussion in 'Community Discussion' started by Eric Lewis, Nov 11, 2007.

1. ### Eric Lewis macrumors 68020

Joined:
Feb 4, 2007
Location:
#1
I am trying to make a circle which is i believe

( x ) ^2 + ( y )^2 = 8

I need to make it smaller and move it up 6 and over to the left 2?

How do i do this?

Thanks

2. ### Jasonbot macrumors 68020

Joined:
Aug 15, 2006
Location:
The Rainbow Nation RSA
#2
To move it horizontally you need to change the p value

To move it vertically you need to change the q value

To make it smaller you need to change the r value

The equation of a circle is:
r^2=(x+p)^2+(y+q)^2

to change p if you subtract from p teh graph moves forward and if you add it moves backwards.
so in the graph we need to change p by a factor of 2 to the left. left is negative so we need to add 2. so (x+2)^2

to change q its the same story. we need to move it up 6 so we subtract 6. so (y-6)^2

so our new equation is 8=(x+2)^2+(y-6)^2

finally to change the graphs size we need to merely change the radius by just changing 8 to anything smaller than 8.

On a side note, I prefer grapher for making graphs in OS X

3. ### siurpeeman macrumors 603

Joined:
Dec 2, 2006
Location:
the OC
#3
it would be easier to go with the same equation with minuses instead of pluses.

r^2=(x-p)^2+(y-q)^2

that way, a positive p-value would represent a positive x movement, and the same with q.

4. ### Jasonbot macrumors 68020

Joined:
Aug 15, 2006
Location:
The Rainbow Nation RSA
#4