Use this fact to find the sign of the slope of the antiderivative at x = -4.
Since the smallest possible triangle will obviously touch the circle with all three sides, make sure you've drawn the base of the triangle as touching the circle, too. Draw a radius line down to this intersection point, labelling as "r".
Draw in the rest of the altitude line for the triangle, labelling the rest of the height as "h", so the total altitude is h + r.
Where you go from here may depend on how much you remember from geometry. What are your thoughts? How far can you get?
Please be complete. Thank you!