# Finding the radius of a circle

• Apr 4th 2012, 08:15 PM
levunit
Finding the radius of a circle
Hey guys I have a question. I'm helping my dad build a desk and he needs to find the radius of a circle created by an arc on the bottom on the desk. The only measurements we have are in this poorly drawn picture below. I tried multiple methods and came up with the answer around 56. I could use some reassurance though, thanks for the help.
• Apr 5th 2012, 12:44 AM
earboth
Re: Finding the radius of a circle
Quote:

Originally Posted by levunit
Hey guys I have a question. I'm helping my dad build a desk and he needs to find the radius of a circle created by an arc on the bottom on the desk. The only measurements we have are in this poorly drawn picture below. I tried multiple methods and came up with the answer around 56. I could use some reassurance though, thanks for the help.

1. I've "completed" your sketch such that you can see that actually you are dealing with a right triangle.

2. In a right triangle the square of the height equals the product of the two hypotenuse segments. With your values:

$(2r-6) \cdot 6 = 40^2$

3. Solve for r. I've got r = 136.33
• Apr 5th 2012, 01:13 PM
levunit
Re: Finding the radius of a circle
Thanks for the help, but may I ask why (2r - 6)*6=1600? I'm a little rusty when it comes to this stuff.

EDIT: Nevermind, I skipped a line. I understand now. Thanks!