# How to find similarity of two series over time containing periodic trends?

Considering the data is received from a streaming source each second.How to distinguish if both the line graphs 'look' same/different in real time, statically, like the picture given below

Edit:
1.Not sure if there is something as real-time periodic correlation mechanism then cross-correlation would perhaps be an ideal solution ?
2. Comparing slope of the two Line is the last option I would go with. 3. If statistically there is no way to solve this then I would look at machine learning to solve this