An example could be limits. We don't do them formally at all, and yet we pretend that we are doing differentiation properly ("from first principles") when all we really do is a bit of algebra and then "by the magic of limits" the answer drops out. #ALevelMaths#ITeachMaths#UKMathsChat

Limits is one of the key underlying concepts we introduce at A level - exploring them and asymptotes in graphical representations helps ensure calculus and later topics link together? Exploring graphs of functions before differentiation feels valuable rather than just going straight into polynomials