Attacking Enemies at an Angle

First: I haven't found anything useful regarding my question. I might have been too clumsy to find it. Sorry if that is the case.

I'm still working on a 2D Game from a 2.5D Perspective, using C# and Unity 5.3.

I wrote a Script with OverlapSpheres to let the player attack his enemies. I haven't found out by not how I can control die angle in which the enemies are hit. For example: If I have a Dagger equipped I only hit enemies right before me, if I have a Greatsword equipped I can hit enemies in a 90° angle in front of my Character.

Thank you all in advance.