Calculus Fundamental Technique

$latex D first, then \int$

This is just a simple but powerful application of Calculus, behind which lies the philosophy of Leibniz:

1. D (=dy/dx) is the inverse function of $latex \int$
2. Calculus Fundamental Technique: $latex D first, then \int$
E.g. Sherlock Holmes example:
1. D first:
dT/dt = k(T-Ts)
=> can't solve directly
2. Take D's inverse:
$latex \int {dT/(T-Ts)} = k.dt$
=> can solve now !