def loads(self, requirements_text):
        lines = re.findall(Requirement.spec_regex,
                           requirements_text,
                           re.MULTILINE)
        for line in lines:
            self.add(Requirement(line[0], "".join(line[1:])))
def getAp1(self):
        ret = math.acos(((self.getLenp2() * self.getLenp2() + self.getLenp3() * self.getLenp3()) - self.getLenp1() * self.getLenp1()) / (2* self.getLenp2() * self.getLenp3()))
        return ret