A geometry problem by Sabhrant Sachan

Geometry Level 2

$\large 81^{\sin^2 x} + 81^{\cos ^2 x} = 30$

Which of the following values is a possible value of $x$ satisfying the equation above?

\dfrac{\pi}4

\dfrac{\pi}3

\dfrac{\pi}2

\dfrac{\pi}{15}

\dfrac{7\pi}{18}

\dfrac{5\pi}{18}