question_answer

If \[\alpha \cos \theta +b\,\sin \theta =m\] and \[\alpha sin\theta -b\,\cos \theta =n\], then the value of \[{{a}^{2}}+{{b}^{2}}\] is

A) \[m+n\]

B) \[m\,n\]

C) \[\sqrt{m\,n}\]

D) \[{{m}^{2}}+{{n}^{2}}\]