How do I remove this piece of triangle

so I’m trying to make realistic range in a tower defense game like in this video: Tower Defense X Juggernaut Update… | ROBLOX - YouTube, i’ve gotten the base concept done.


in the image, i dont really like how theres a piece of triangle sticking out to reach to the center of the circle. i would like ideas on how i could calculate the size and position of a part to subtract async the triangle, so the triangle does not have a piece that extends pass the blockage.

What?
I don’t understand, could you elaborate a bit mbit more?