Answer:
[tex]7 \pi\ mm[/tex]
Step-by-step explanation:
we know that
The circumference of a circle is equal to
[tex]C=2\pi r[/tex]
In this problem we have
[tex]r=21\ mm[/tex]
substitute
[tex]C=2\pi (21)=42\pi\ mm[/tex]
[tex]360\°[/tex] subtends the complete circle of length equal to [tex]42\pi\ mm[/tex]
so by proportion
Find the length of arc which a central angle of [tex]60\°[/tex]
[tex]\frac{42\pi}{360}\frac{\ mm}{degrees}=\frac{x}{60}\frac{\ mm}{degrees} \\ \\x=42\pi *60/360\\ \\ x= 7 \pi\ mm[/tex]
