A team of engineers were required to measure the height of a flag pole. They only had a measuring tape, and were getting quite frustrated trying to keep the tape along the pole. They’d get it a bit up the pole, but then the tape would buckle and it would fal down.
A mathematician comes along and listens to their problem. After inspecting both the tape measure and the flag pole, he proceeds to remove the pole from its base in the ground. He lays it down flat, measures it easily with the tape measure, and then resets the pole in the ground.
When he leaves, one engineer says to the other and sighs. “Just like a mathematician! We need to know the height, and he gives us the length!”