def read(fname):
    return open(os.path.join(os.path.dirname(__file__), fname)).read()
def getAp3(self):
        ret = math.acos(((self.getLenp1() * self.getLenp1() + self.getLenp2() * self.getLenp2()) - self.getLenp3() * self.getLenp3()) / (2* self.getLenp1() * self.getLenp2()))
        return ret