I am attempting to calculate unknown points based off a known point and the percentage of two prior points range. Following is the formula.
Point A (A1) - Unknown
Point B (B2) – Unknown
Point C (C1) – Known value = A1 + ((B2-A1)*.618)

I also may have one or both of the following:
Point D (D1) = C1 - ((C1-B2)*.618)
Point E (E1) = C1 - ((C1-B2)*.382)
Is there a way to determine A1 and B1?
Thanks