Fundamental Theorem of Calculus: Difference between revisions

In the case of a particle traveling in a straight line, its position, ''x'', is given by ''x''(''t'') where ''t'' is time and ''x''(''t'') means that ''x'' is a function of ''t''.  The derivative of this function is equal to the infinitesimal change in quantity, d''x'', per infinitesimal change in time, d''t'' (of course, the derivative itself is dependent on time).  This change in displacement per change in time is the velocity ''v'' of the particle. In Leibniz notation:

Rearranging this equation, it follows that:

By the logic above, a change in ''x'' (or Δ''x'') is the sum of the infinitesimal changes d''x''.  It is also equal to the sum of the infinitesimal products of the derivative and time.  This infinite summation is integration; hence, the integration operation allows the recovery of the original function from its derivative. It can be concluded that this operation works in reverse; the result of the integral can be differentiated to recover the original function.