How do I compare degrees to dot product?

I’m working on melee targeting, and I can get the angle of an enemy’s facing relative to his enemy by taking the dot product, which gives me a number between 1 and -2. Ideally, I would like to feed my function an attack radius in degrees, which represents an imaginary cone extending out from the player’s feet aligned along their forward facing. So if I run TargetingFunction(30), enemies within 15 degrees left or right of my forward vector should be hit.

Where my brain is failing to brain is on the math- given a dot product for the enemy, and a degree cone for the attack AoE, how do I translate the cone into terms I can compare directly with something like if(dProduct

You can put rad2deg like this example to change to degrees

float rotZ = Mathf.Atan2 (diffrance.y, diffrance.x) * Mathf.Rad2Deg;

Hope this is some help.