Using the formula to calculate the arc length
[tex]\text{arc length}=\frac{\theta}{360}\cdot2\pi r[/tex]
where θ is the angle and r is the radius
In this case
θ=120
r=18/2=9
we substitute the values in the formula
[tex]\text{arc length =KL}=\frac{120}{360}\cdot2\pi(9)=6\pi[/tex]
