### Question:
AngleCalc { static final double atan2( double y, double x ) { double absY = Math.abs(y) + 1e-10; double r, angle; if (x < 0.0) { r = (x + absY) / (absY - x); angle = PI3_4; } else { r = (x - absY) / (x + absY); angle = PI_4; } angle += (0.1963 * r * r - 0.9817) * r; if (y < 0.0) return -angle; return angle; }  double calcOrientation( double lat1, double lon1, double lat2, double lon2 ); double convertAzimuth2xaxisAngle(double azimuth); double alignOrientation( double baseOrientation, double orientation );  }### Answer:
@Test public void testAtan2() { assertEquals(45, AngleCalc.atan2(5, 5) * 180 / Math.PI, 1e-2); assertEquals(-45, AngleCalc.atan2(-5, 5) * 180 / Math.PI, 1e-2); assertEquals(11.14, AngleCalc.atan2(1, 5) * 180 / Math.PI, 1); assertEquals(180, AngleCalc.atan2(0, -5) * 180 / Math.PI, 1e-2); assertEquals(-90, AngleCalc.atan2(-5, 0) * 180 / Math.PI, 1e-2); assertEquals(90, Math.atan2(1, 0) * 180 / Math.PI, 1e-2); assertEquals(90, AngleCalc.atan2(1, 0) * 180 / Math.PI, 1e-2); }