I always understood the memorization part as a stopgap to truly understanding them. In the same sense that doing this work by hand will build depth of understa

I always understood the memorization part as a stopgap to truly understanding them. In the same sense that doing this work by hand will build depth of understanding, I know that remembering the trig identities came before really understanding their relationships. And that also came far before I could truly understand Euler's formula, radians, etc.