\(A= \dfrac{r}{2l}\) \(\text{Equation}\)
\(A= \dfrac{rl}{2}\) \(\text{Simplify Equation}\)
\(A*2=rl\) \(\text{Multiply both sides by 2}\)
\(2A=rl\) \(\text{Regroup terms}\)
\(\dfrac{2a}{r}=l\) \(\text{Divide both sides by r}\)
\(l=\dfrac{2a}{r}\) \(\text{Solution}\)
