"My shower lacks pressure so I want to replace the existing 1/2 inch
copper
pipe that leads up to it with 3/4 inch copper pipe. Obviously, if done

correctly this will increase the water pressure available at my
shower."

The first paragraph of your post is incorrect and untrue. It makes me
wonder how you could be so judgemental of everyone's response when you
don't have a clue of what your asking yourself.

kenny b