In most geometry courses, we learn that there's no such thing as "ssa congruence". that is, if we have triangles abc and def such that ab=de, bc=ef, and ∠a=∠d, then we cannot deduce that abc and def are congruent. however, there are a few special cases in which ssa "works". that is, suppose abc is a triangle. let ab=x, bc=y, and ∠a=θ. for some values of x, y, and θ, we can uniquely determine the third side, ac.(a) use the law of cosines to derive a quadratic equation in ac.(b) use the quadratic polynomial you found in part (a) in order to find conditions on x, y, and θ which guarantee that the side ac is uniquely determined.