Getting +180 / -180 degrees between two vectors

Hello everyone. Potentially basic math question from someone who’s not really good at math at all.

I need to calculate the angle between my Player camera’s Forward Vector and a point in the world (for this test, 0,0,0). I’m at this point right now thanks to some google searching and my knowledge of math:

And this is an illustration of what I expect:

125982-screen02.jpg

Hope this makes sense. Thanks for the help!

Edit: To clear up a couple things, this is for a 2D radar UI I have. The “objective arrow” is my UI element that rotates based on the rotation angle. Also, because this is a 2D radar, I’m flattening everything to 0 height, that’s why I’m making vectors with the Z set to 0 (I could also compare the Z values to add an upper or lower value later on to tell the player whether the objective is higher or lower than the player, but don’t need that for now).