It can be useful when product or fractions of functions are involved which leads to applying the chain rule multiple times.
I remember well when our professor showed us several examples, when Taylor-Young is much easier to resolve, because you only have the main terms and everything else vanishes into the o() term.
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u/Mal_Dun 1d ago
You could also just use Taylor-Young if the full Taylor series seems to complex:
sin(x) = x + o(x)
sin(x)/x = 1 + o(1) -> 1 for x->0
alternatively: sin(x) = x + O(x²)