N/S calling all smart people

Ok so I had a question creep into my head the other day after consuming a few beers. Everyone knows that a potential tackler has a better shot at tackling a runner by taking an angle at the runner. But according to the Pythagorean Theorem that we all learned in fifth grade, the angle, C,(that the tackler is taking) is a longer distance than what the runner, B, would be taking. My question is how does it give the tackler a better chance at catching up if the distance he has to travel is greater than what the runner's is? I can't come up with an answer.