An extension of the Pythagorean Theorem is the so-called distance formula.
d^2=(x2-x1)^2+(y2-y1)^2, letting east/west be x, north/sout be y and east and north be positive
d^2=(1--2)^2+(2--1)^2
d^2=3^2+3^2
d^2=9+9
d^2=18
d=√18 mi.
d=√(9*2) mi.
d=3√2 mi.
d≈4.24 mi. (to nearest hundredth of a mile)
