OK. That's definitely Euclidean Geometry.
No worry, there's no need to be a champion in this field, I think. No one is interested in seeing if a professor of Theoretical Physics can prove a theorem of Euclidean Geometry.
However, if you are so interested in Theoretical Physics and if you are good at Maths, I really think that you don't LIKE it because you have had a wrong approach, of something similar.
Einstein said that if someone is not impressed by the building of Euclidean Geometry, they are not inclined to be theoretical scientists. Obviously, Einstein's ideas are not necessarily true.
To my mind, if you start with a good book and you start right from the beginning, you will have a lot of fun with Euclidean Geometry. Moreover, once understood, there's nothing to remember. I also think I will study Theoretical Physics(though perhaps not one of the most popular branches), and this kind of Geometry has always been my favourite subject OF ALL when I was ay high school.
Are you still at high school? I think so, as you are studying this stuff, though educational system may be very different. Where do you live, if you do not mind me asking? I do not think this geometry is studied at university in any European Country(in Maths or Physics), even though someone who does not even understand what is a triangle and its basic properties(or similar basic stuff) is surely not a strong candidate for a Physics degree!
As far as the other kind of geometry we reffered to, I do not know how to specify further, but it's the kind of stuff that starts with linear algebra(indispensable for Quantum Mechanics), and then develops in tensor calculus, differential geometry and Riemannian Geometry(the language of General Relativity). It's not strongly connected to triangles, circles and squares, it's all abstract mathematical concept, but, again, try to approach Euclidean Geometry in the right way.
You will have a lot of benefits from it. Remember also what Einstein said: though not necessarily true, there must be a reason why it's been handed down to us.
NOTE: I am only a bachelor student in Physics, but I have tried to explain my opinion.