It's a net loss if you just memorise them as isolated curiosities and use them to do a job that a calculator could do better, but it's a net gain (I'd argue eve

It's a net loss if you just memorise them as isolated curiosities and use them to do a job that a calculator could do better, but it's a net gain (I'd argue even an absolute gain) if it introduces you to the idea, all the more relevant in the age of high-powered, fast computers, that sometimes there's a cleverer way to do something than brute force.