Referenced from lesson The Distance Formula (Spring, 2021)
Distance between the pyret and the boot:
num-sqrt(num-sqr(line-length(9, -3)) + num-sqr(line-length(3, -2)))
Explain how the code works.
Now write the code to find the distance between this boot and pyret.
These materials were developed partly through support of the National Science Foundation,
(awards 1042210, 1535276, 1648684, and 1738598). 
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