A long straight wire carries a current i along the x-axis. Consider the points A(0,1,0), B(0,1,1), C(1,0,1) and D(1,1,1,)

The magnetic field at D has magnitude $B=\frac{{\mu }_{0}i}{2\sqrt{2}\pi }$

Points A and C have magnetic fields of same magnitude

The magnetic field at D makes an angle of  with the xy plane 

Points B and C have magnetic fields of same magnitude