# DO you think this is real?

1. Mar 7, 2010

### LucasGB

Do you guys think this really works?
http://www.xamuel.com/inverse-graphing-calculator.php [Broken]
I wasn't able to verify it with my graphing software.

Last edited by a moderator: May 4, 2017
2. Mar 8, 2010

### Mentallic

It looks incredible! Really mind-boggling!
I always wondered if words and pictures could be made out of equations in cartesian form.

I tried the letter O which should have just been a circle radius 1 unit centre (3,3) by the looks of it, and this is what it gives:

$$\left((x-3)^2+(y-3)^2-1\right)^2+\left(y^2-6y+8+\sqrt{y^4-12y^3+52y^2-96y+64}\right)^2=0$$

Now, the first part is the correct equation for the circle, but what's this extra nonsense that's tacked on?

3. Mar 8, 2010

4. Mar 8, 2010

### Mentallic

Last edited by a moderator: Apr 24, 2017
5. Mar 8, 2010

### LucasGB

So it works?

6. Mar 8, 2010

That expression is added to the formula'' for words and sentences as well. Perhaps it's important to the work; perhaps it's a private joke by the programmer.

7. Mar 8, 2010

### Mentallic

Yes I believe it does work. And once you start to realize the pattern (go for 1 simple letter at first, such as O and X and work your way from there), it's not as unbelievably impossible as you first might have thought - including myself.

8. Mar 8, 2010

### DrGreg

If you look at the structure of the equation for several letters, you will see a pattern emerging, e.g. for 3 letters

$$z_1^2 \, z_2^2 \, z_3^2 \, + \, w^2 \, = \, 0$$​

where z1 is a formula for the first letter, z2 is a formula for the second letter, z3 is a formula for the third letter, and w is always the same each time, and all of them functions of x and y.

Note that the equation is true if and only if w is zero and at least one of the other expressions is zero.

w is zero if $2 \leq y \leq 4$ and otherwise non-zero, so the effect of adding w2 is to prevent any curves being drawn above y=4 or below y=2. In the case of a circle ("O") it doesn't matter, but for some of the other letters, the formula given creates the correct symbol between heights 2 and 4 but also creates extra lines outside that range, so adding w2 suppresses the unwanted lines.

9. Mar 8, 2010

### Tac-Tics

10. Mar 8, 2010

### uart

Nice explaination of the mysterious extra term. Thanks DrGreg. :)

11. Mar 8, 2010

### Mentallic

Yeah, nice explanation DrGreg!

I also cannot comprehend why every term is being squared. What is the effect of this?