# Thread: need help with angle-circle relationship rules

1. ## need help with angle-circle relationship rules

Hello Math Help Forum!

I'm making geometry flash cards based on the book "Advanced Euclidean Geometry" and the software "Geometer's Sketchpad." By the way, Geometer's Sketchpad has accompanying books that show you how to use GS for Geometry, Dynamic Algebra, Trig, Calc and even statistics. It's a pretty easy tool to use, I've figured out how to make 2 dimensional geometrical figures and measure them. One thing i haven't figured out how to do is how to specify the exact angles and distances that I specify and have GS make the figure. GS is also a very fancy graphign calculator. You can get a trial version or buy a 1 year license for 10 here:

Home - The Geometer's Sketchpad Resource Center

So I got a geometry question, based on this figure:

1. The measure of an inscribed angle is one-half the measure of its intercepted arc.

So the angle is 25.84 degrees, and the arc is 3.27cm. These are apples and oranges! How can an inscribed angle in degrees be half of an intercepted arc in centimeters? Do I convert to radians and multiply by pi? I tried that and got 1.41 which isn't close to 3.27.

Anyway, thanks to anyone who helps!

2. ## Re: need help with angle-circle relationship rules

I don't know what you are trying to find.
That said,
$\frac{{2m\left( {\angle CAB} \right)}}{{{{360}^o}}}$ is the percent of the circumference, $2\pi r$, represented by the measure of the arc.

3. ## Re: need help with angle-circle relationship rules

THanks Plato! It turned out that finding distance of arc was not possible, I was supposed to be looking for the degrees of arc.

By the way, what's the m stand for in your equation?

4. ## Re: need help with angle-circle relationship rules

Originally Posted by Robwinfield
By the way, what's the m stand for in your equation?
measure

5. ## Re: need help with angle-circle relationship rules

Originally Posted by Plato
I don't know what you are trying to find.
That said,
$\frac{{2m\left( {\angle CAB} \right)}}{{{{360}^o}}}$ is the percent of the circumference, $2\pi r$, represented by the measure of the arc.
OK, so if I read this correctly, it is 2 times the measure of angle CAB divided by 360 degrees?