Comment by seanhunter

They may have learned mechanics by studying Newton but they can’t have learned calculus. Principia includes geometric series and limits etc but given as geometric arguments so you don’t come out of newton’s principia knowing how to do calculus. If they learned the method of fluxions from Newton (which is equivalent to calculus) then I feel very sorry for them missing out on the far better modern presentation of Leibnitz’s calculus that they would get in studying say Spivak or Stewart or any other modern textbook. For the same reason everyone teaches Taylor series (which are fantastically useful) rather than Newton’s wildly inferior series derivation which he used because Taylor series hadn’t been (re)discovered yet.[1]

Euclid isn’t surprising. School children used to learn plane geometry from Euclid until the 1950s or so. I learned geometry at school using a syllabus from Euclid and we learned the modern form of Euclid’s postulates etc but we didn’t study Euclid itself.

[1] Taylor series were developed in the modern form by James Gregory who was trying to reverse engineer how Newton had come up with his series expansions. I say rediscovered above because they were first written down by Madhava of Sangamagrama who gave Taylor series expansions for the trigonometric functions and natural logarithms/exponential function in the 14th century.