I have the following equation -

and am required to use it for the problem -I'm having difficulty getting my head around the problem and understanding how the discriminant is useful to finding the solution. I'm sure it's something simple I'm just not seeing and I'll kick myself for not thinking of it when someone enlightens me. Any assistance would be greatly appreciated."Use the discriminant to find the domain for which the angle θ is acute."

Thank you,

- deSitter