1. straight line
So, even a straight line, defined with calculus, is a curve.
Englisch Wort "prosta linia"(straight line) tritt in Sätzen auf:
angielski rozdział 22. beeline
The kids made a beeline for the TV.
As soon as work is over, he makes a beeline for the pub.
Make a beeline for Mike. He is looking forward to you. At parties he always makes a beeline for the prettiest woman in the room.
If you want to go there in time, you'd better make a bee-line for your class right away.
3. solid line