@Test
public void toStringPrintsAngle() {

    final Obtuse<Double> obtuse = new Obtuse<>();
    final Double angle = obtuse.resolve(new MkProduct<>()).doubleValue();
    final int precision = 6;
    MatcherAssert.assertThat(
        obtuse.toString(),
        Matchers.containsString(
            Double.toString(angle * 2 / Math.PI - 1).substring(0, precision)
        )
    );
}