Vector Length

Given a vector V with tail at the origin and head at b = (x_b, y_b), what's its length?

According to Pythagoras, the length of the hypoteneuse is the square root of x_b² + y_b².

You can move b around and calculate the length of a few favored vectors. But suppose you come across a vector whose tail is not so nicely situated?

Apply Pythagoras again.