Writing a formula from a circle and triangle

• April 6th 2010, 09:55 PM
krzyrice
Writing a formula from a circle and triangle
http://i41.tinypic.com/rii6pt.jpg

I need help with part a. I don't understand how to write the formula. Please explain and show to me step by step on how to do this problem. Thanks.
• April 6th 2010, 10:11 PM
Stroodle
To find $d$ you can use pythagorus' theorem. The hypotenuse is $x+r$, and the other side is $r$. Then note that $\theta=tan^{-1}\left ( \frac{d}{r} \right )$.
• April 6th 2010, 10:17 PM
krzyrice
What about theta in that formula? How would I find out what that is in order to find d?
• April 6th 2010, 10:25 PM
Stroodle
It's asking for $d$ in terms of $x$ and $r$. You don't need theta for this part of the question:

$d=\sqrt{(x+r)^2-r^2}$

You can simplify this formula.