At which angle must the two forces (x+y) and (x-y) act so that the resultant may be $\sqrt{\left({\mathrm{x}}^2+{\mathrm{y}}^2\right)}$

• A

  ${\cos }^{-1}(-\frac{{\mathrm{x}}^2+{\mathrm{y}}^2}{2({\mathrm{x}}^2-{\mathrm{y}}^2)})$

• B

  ${\cos }^{-1}(-\frac{2({\mathrm{x}}^2-{\mathrm{y}}^2)}{{\mathrm{x}}^2+{\mathrm{y}}^2})$

• C

  ${\cos }^{-1}\left(\frac{{\mathrm{x}}^2+{\mathrm{y}}^2}{{\mathrm{x}}^2-{\mathrm{y}}^2}\right)$

• D

  ${\cos }^{-1}(-\frac{{\mathrm{x}}^2-{\mathrm{y}}^2}{{\mathrm{x}}^2+{\mathrm{y}}^2})$