I beg to differ. One of my most vivid educational experiences is of my teacher calculating approximate square root on the side of the blackboard when he needed

I beg to differ. One of my most vivid educational experiences is of my teacher calculating approximate square root on the side of the blackboard when he needed it for something completely unrelated. To me it felt like he was riding a unicycle or swallowing a sword. Seeing that the audience was perplexed, he reluctantly took a five minute detour and explained Newton-Raphson algorithm, at which point the unbelievable circus trick suddenly became trivial.