question_answer

If \[m=a\,{{\cos }^{3}}\theta +3a\,\,\cos \theta {{\sin }^{2}}\theta ,\] \[n=a{{\sin }^{3}}\theta +3a\sin \theta .{{\cos }^{2}}\theta ,\] then the value of \[{{(m+n)}^{\frac{2}{3}}}+{{(m-n)}^{\frac{2}{3}}}\] is:

A)  0                                

B)  1

C)  2a                               

D)  \[2{{a}^{\frac{2}{3}}}\]

E)  None of these