# Monday, May 15

In class students worked through problems intended to help them create the distance formula

$\dpi{300}\inline d^2 = (x_1 - x_2)^2 + (y_1 - y_2)^2$

which becomes

$\dpi{300}\inline d = \sqrt{(x_1 - x_2)^2 + (y_1 - y_2)^2}$

They should understand how and why the formula works. And also see the relationship between the distance formula and the pythagorean theorem which it is based on

a triangle is right if and only if (its sides a, b and c) satisfy $\dpi{300}\inline a^2 + b^2 = c^2$