Bro, dude, chum, I think the first graph is another example, unrelated to the maths above.
Short answer: You can't get the first figure from anywhere. It's an example.
Poor slide? Yes.
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It appears that he has not defined the membership function {} used in the maths. I can't see any obvious definition that leads to a graph similar to the lower graph. Conclusion: they are not related. Just two separated examples of using MAX() as union of fuzzy sets.