Q find in radians, all the values of $\displaystyle \theta$ between $\displaystyle -\pi and \pi$ satisfying the equation

$\displaystyle 8cos^2\theta+2sin\theta=7$

the answers are 0.524 2.261 which i get but i dont get 3.386 or 6.034 instead i get -14.5 degrees and hence 180-14.5 can any see where I have gone wrong or is it the answers thnx.!