I have several questions that I am seeking clarification on. The first 2 are rather simple: 1) The formula for r describes the blue streamline (the stagnation streamline) right? (Just confirming) 2) I assume that the stagnation streamline is called so because it passes through the stagnation point? 3) What is the difference between Ψ = +πm and πa ? They both seem to refer to the same thing? I mean the distance from the y=0 to the top of the stagnation stream line is equal to both +πm and πa ? 4) Why does rsin(theta) = πa ? I know that rsin(theta) = y and y = πa but what is the significance of labelling the vertical distance as rsin(theta)? Any specific reason behind this?