9 Replies Latest reply: Jun 10, 2013 9:16 AM by ecm1
Level 1 (0 points)

When using Grapher what equation must I use to be able to graph a specific circle segment? Using y^2+x^2 will graph a complete circle, and using

y=sqrt(4-x^2) will give me a semi-circle, but what equation must I use to get any other segment, like for a 45˚, 66˚, 152˚, or any segment between 0˚ and 360˚.?

Would greatly appreciate the help. I am a senior, just toying around with this.

Thanks.

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iMac, OS X Mountain Lion (10.8.4)
• ###### 1. Re: When using grapher what equation must I use to graph a circle segment? I can graph a circle and semi-circles but not any other segment..
Level 10 (116,475 points)

Hello, math was one of my weaker points, but the reason y=sqrt(4-x^2) shows a half circle is that it's only drawing positive values of y, there's likely some way to only draw positive values of x also to get a 90° arc, but I think we'd need to use sine, radians, or such, but too distant for me to figure it out!

• ###### 2. Re: When using grapher what equation must I use to graph a circle segment? I can graph a circle and semi-circles but not any other segment..
Level 1 (0 points)

Thanks anyway. BTW the y=sqrt(4-x^2) gives a semi-circle in the 1st and 2nd quadrants, but when you make the equation a negative - like y=-sqrt(4-x^2) - it gives a semi circle in the 3r and 4th quadrants.

thanks

• ###### 3. Re: When using grapher what equation must I use to graph a circle segment? I can graph a circle and semi-circles but not any other segment..
Level 10 (116,475 points)

I think the formula in a different language is...

th = 0:2*pi/nsegments:2*pi;

xunit = r * cos(th) + x;

yunit = r * sin(th) + y;

If you can figure out how to do that in Gtapher...

• ###### 4. Re: When using grapher what equation must I use to graph a circle segment? I can graph a circle and semi-circles but not any other segment..
Level 2 (200 points)

Hi ecm1,

Use parametric equations as in attachment.

Enjoy,

YB24

• ###### 5. Re: When using grapher what equation must I use to graph a circle segment? I can graph a circle and semi-circles but not any other segment..
Level 10 (116,475 points)

Thanks!

• ###### 6. Re: When using grapher what equation must I use to graph a circle segment? I can graph a circle and semi-circles but not any other segment..
Level 1 (0 points)

Looks like the right way to go, Will try.

Thanks.

• ###### 7. Re: When using grapher what equation must I use to graph a circle segment? I can graph a circle and semi-circles but not any other segment..
Level 2 (200 points)

A little more from YB24 :

• ###### 8. Re: When using grapher what equation must I use to graph a circle segment? I can graph a circle and semi-circles but not any other segment..
Level 1 (0 points)

Thanks very much for all the time you spent on this. It is really great.  Will give it a go immediately.

Once again, thank you.

ecm1

• ###### 9. Re: When using grapher what equation must I use to graph a circle segment? I can graph a circle and semi-circles but not any other segment..
Level 1 (0 points)

Hi Saint YB24 - I've played with this all morning; it's great. Exactly what I was looking for.

Thanks a million. I definetly owe you a beer for that one.

Thanks again.

ecm1