i want write a program to calculate distance using formula below:
d = acos(sin(Lat1) × sin(Lat2) + cos(Lat1) × cos(Lat2) × cos(Lon1 – Lon2))

but, i find that vb6 not support "acos". how to solve this problem?

also how to write formula below in vb.

rad_dist = atan(-t5 / sqrt(-t5 * t4 + 1)) + 2 * atan(1)

how to write sqrt in vb code.