# Oppgave 1
from math import pi

class Sirkel:

    def __init__(self, radius):
        self._radius = radius

    def diameter(self):
        return 2*self._radius

    def omkrets(self):
        return self.diameter()*pi #alt: bruk 3.14

    def areal(self):
        resultat = pi*self._radius**2
        return resultat