Answer
59 degrees below the horizontal
Work Step by Step
To find the direction of the acceleration vector we need to make a triangle with the x and y components as the two legs. To find the direction, we need to find the angle it makes with the horizontal which can be found by
$tan(\theta) = \frac{y}{x} $ and therefore $\theta = arctan(-10/6) = -59^{\circ} $
