Equation (1.28):

Equation (1.30):

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Let be a path-independent function and be a path-dependent function; then

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— 1.5.1 Varying a path

— Structure and Interpretation of Classical Mechanics

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Assume that is a path-independent function, so that we can use Eq. 1.26:

Assume that is a path-independent function, so that any value of depends on the value of at that moment only, instead of depending on the whole path :

What kind of product is it here? Is it just a dot product? Probably not.

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— Me@2019-10-12 03:42:01 PM

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2019.10.13 Sunday (c) All rights reserved by ACHK