pub fn from_angle_x<A: Into<Rad<S>>>(theta: A) -> Matrix3<S> {
        // http://en.wikipedia.org/wiki/Rotation_matrix#Basic_rotations
        let (s, c) = Rad::sin_cos(theta.into());

        #[cfg_attr(rustfmt, rustfmt_skip)]
        Matrix3::new(
            S::one(), S::zero(), S::zero(),
            S::zero(), c, s,
            S::zero(), -s, c,
        )
    }
Create a rotation matrix from a rotation around the `x` axis (pitch).
src/matrix.rs