Question
If $u = \sqrt {{a^2}{{\cos }^2}\theta + {b^2}{{\sin }^2}\theta } + \sqrt {{a^2}{{\sin }^2}\theta + {b^2}{{\cos }^2}\theta } $
then the difference between the maximum and minimum values of ${u^2}$ is given by :
then the difference between the maximum and minimum values of ${u^2}$ is given by :