pi -- a constant with the value 3.14159
pi is 3.14159265359 (well at least for yab); do not try to assign to pi (e.g. pi=22/7)this would not only be mathematically dubious, but would also result in a syntax error.
for a=0 to 180
print "The sine of ",a," degrees is ",sin(a*pi/180)
This program uses pi to transform an angle from degrees into radians.