how do you find the arc length of a semi-circle?

the arc length is calculated by the formula [tex]\displaystyle\bf C=\frac{2\pi r}{360} \cdot\alpha[/tex] then [tex]\displaystyle\bf C=\frac{2\cdot 8 \pi }{360} \cdot180=8\pi=3,14\cdot8=25.12[/tex] or it can be calculated using the circumference of the circle since we have a semicircle the circumference 2πr must be divided by 2 С=2πr:2=πr =8π=25,12