Find the length of the line segment shown below.

Question

Answer 1

One could use the distance formula here but I think it’s easiest to visualize a triangle made with the y axis and the line y=4. The two legs of this now right triangle have length 5 and 9 units. Using the Pythagorean theorem we get a line segment of length sqrt(5^2 + 9^2) = sqrt(106).