Hello, I am a beginner using Mathematica. I would like to know how to express for example a function that depends on three variables and to calculate it using a IF BLOCK. I have the following function: a(y,w,d)=(acos((w-y)/d)*d^2-sin(acos((w-y)/d))*(w-y)*d) and I want to evaluate it, to evaluate this function I have to write a IF BLOCK like the following IF (w-y)<d then IF (w-y)>0 then Gnuplot muss evaluate a(y,w,d) else is pi*d^2 else cero. I have attempt it. But only it works when I put a(y,w,d) if only depends on y, but it depends also from w and d. Might anybody help me?