Coba jelasin Lihat juga dari Kamiran dalam bahasa melayu dong

. In particular chapters III and IV.

(Originally published by Cambridge University Press, 1897, based on J. L. Heiberg's Greek version.)

The Integrator by Wolfram Research

Riemann Sum by Wolfram Research

Mathematical Assistant on Web online calculation of integrals, allows to integrate in small steps (includes also hints for next step which cover  techniques  like by parts, substitution, partial fractions, application of formulas and others, powered by Maxima (software))