help please!

The angle \(\displaystyle \theta\) through which a point revolves in radians is defined the ratio of the distance \(\displaystyle d\) along the arc to the radius \(\displaystyle r\):

\(\displaystyle \theta=\dfrac{d}{r}\)

What is the distance all the way around a circle (the circumference), in terms of \(\displaystyle r\)?
 
Top