SQRT of (40-40)^2+(18-60)^2
= SQRT of (0)^2+(-42)^2
= SQRT of -42^2
= 42
negative numbers squared = postitive numbers.
you cant square a number and bring back a negative result
eg 1^2 = 1
-1^2 = 1
SQRT(1) = 1
SQRT(-1) = j (that's an imaginary (not real) number)