What I'd like to do is make the top sides straight horizontals, with the 10deg curved verticals and rounded corners on the top left and bottom right. When I tried doing this by drawing a straight line off the end of the quarter circle, it produced a bump where it connects.
In other words, how can I make a curve that perfectly matches an angled line, the same way the quarter circle in the first image perfectly matches a straight vertical line?
If it requires the use of the pen tool, how can I make sure it is mathematically correct?