Respuesta :

[tex]\bf \textit{circumference of a semicircle}\\\\ C=\pi r~~ \begin{cases} r=radius\\ -----\\ r=9 \end{cases}\implies C=9\pi [/tex]
geerky42
Perimeter of a semicircle would be half of circumference plus diameter.

So that would be P = πr + 2r

Now substitute r to 9 and we have 9π + 2·9 ≈ 9·3.14 + 18 = 46.26

Final answer: 46.26 mm