Determine if two lines are converging or diverging

Question

We have two lines that have corresponding values. We have to know if the lines are converging or diverging in nature.
What mathematical approach can help us understand if these lines are converging or diverging? Please refer to the following picture of the two lines. We have already used slope as an approach which doesn't give information about the entire trend.
Please refer the picture here

Answer 1

As far as I understand, you have two different ways to calculate moving averages from the same data. The orange line is more based on recent data, and thus will react quicker to changes in the data. The green line takes older data points more into account, and thus reacts slower. Thus, whenever the data points are decreasing over longer periods of time, green is above orange, and vice versa if the data points are increasing over longer periods of time. Thus, what you really ask is if your data points will continue to increase (when ignoring small short term fluctuations/noise). Clearly, this cannot be answered from the two curves, as these curves only document the past behavior of the data but don't predict their future behavior.

Answer 2

The moving average over the $n$ past days is essentially a smoothened guess for the value $\frac n2$ days ago: $\frac{1+2+3+4+5}5$ equals $3$ instead of $5$, for example. With exponential instead of arithmetic moving averages, the computation is different, but still the result tends to "lag" behind by a timespan proportional to the length of the moving average. Hence, the 13-day average is greater than the 21-day average during a growth phase and below it during a shrinkage phase, and they cross somewhere near the switch from one phase to another - whether/how often/when such switches occur is unpredictable (or else I'd be rich).