question_answer

If \[0\le x\le \frac{\pi }{2}\] and \[{{81}^{{{\sin }^{2}}x}}+{{81}^{{{\cos }^{2}}x}}=30,\] then x is equal to _______.

A)  \[\frac{\pi }{2}\]                                   

B)  \[\frac{\pi }{3}\]

C)  \[\frac{\pi }{5}\]                                   

D)  \[\frac{\pi }{4}\]

E)  None of these