This is a catenary equation used to calculate the tension of a tower guying cable from the visual sag in the cable. It is based on the length of the base distance from anchor to tower (L), the height of guy cable attachment point on the tower (H), the weight and length of the guy cable, contained in (W), and the tension (T) in the cable for the amount of sag as defined by the intercept distance (I). The intercept distance (I) is that distance to a point on the tower below the guy attachment height, as visually observed on the tower using a surveyor's transit telescope attached to the guy cable at the anchor, to establish the guy starting angle and amount of sag resulting after tensioning.
I'm trying to solve for the individual values of I, H, and L by rearranging the tensioning equation.

Your help in restoring this ol' fogies appreciation for mathamatics would be sorely welcome.