# Math Help - Finding the radius of a circle

1. ## 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.

2. ## Re: Finding the radius of a circle

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

3. ## 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!