3       radian = 180/3.14159265
5       az1 = expr()/radian
10      el1 = expr()/radian
20      az2 = expr()/radian
30      el2 = expr()/radian
40      alpha = az1-az2
50      cosa = sin(el1)*sin(el2) + cos(el1)*cos(el2)*cos(alpha)
60      dist = atn((1-cosa^2)^.5 / cosa) * radian * 3600
70      print dist
80      goto 3
run
