Formula node undefined variables

[Hypnotoad]

im having programming issues with formula nodes. It says i have undefined variables and I defined everything.Can someone please.

h=50;
v=5;
a=4.9L/v**2;
b=h/L;
x=((0.5-ab)/a**2)+sqrt((((0.5-b)/ab**2)**2)-(((b**2)+1)/a**2));
y=((0.5-b)/a**2)-sqrt((((0.5-ab)/ab**2)**2)-(((b**2)+1)/b**2));
A=acos(1/sqrt(x**3));
B=acos(1/sqrt(y**3));