# [SOLVED] I desperately need help

• Jun 12th 2006, 02:56 PM
CSP
[SOLVED] I desperately need help
I have a math exam in 2 days. i havent done the course, but my friend has tutored me , and i seem to know enough of the cirriculum to move on to the program i want next year. However, I do not know how to find the radius of a triangle. Can anyone help me ?
• Jun 12th 2006, 03:14 PM
Jameson
I'm sorry to say I'm not familiar with the radius of a triangle. I even looked it up on Wikipedia to make sure I'm not confusing syntax. Can you give an example of what you mean?

http://en.wikipedia.org/wiki/Triangle
• Jun 12th 2006, 06:00 PM
ThePerfectHacker
Quote:

Originally Posted by CSP
I have a math exam in 2 days. i havent done the course, but my friend has tutored me , and i seem to know enough of the cirriculum to move on to the program i want next year. However, I do not know how to find the radius of a triangle. Can anyone help me ?

I do not know what "radius of triangle" means.
However, I belive I might know what you are referring to.

Radius of Inscribed circle in Triangle" In that case we have that,
$r=\frac{A}{S}$ where $A$ is area and $S$ is semiperimeter. (Note to find area of triangle you might need to used some other theorems).

Radius of Circumscribed circle around triangle: In that case use the extended law of sines:
$2R=\frac{a}{\sin \alpha}=\frac{b}{\sin \beta}=\frac{c}{\sin \gamma}$. (Note to find the angle of the triangle you might need to use the law of cosines to solve for angle).