Liebniz.
Integral calculus was invented in the 17th century with the independent discovery of the fundamental theorem of calculus by Newton and Leibniz.
Greece
Sir Isaac Newton. He and Leibniz both invented the calculus independently.
Newton and Leibniz simultaneously and independently invented calculus.
discovered
Calculus was invented or rather can be detailed as back as 1820 B.C. when the Egyptians used it in order to calculate the volume of the pyramidal frustum
Newton Invented it for his theory of gravity.
Calculus was invented to solve physics problems, so the importance of studying calculus is to solve physics problems.
If you mean "who invented calculus", then Isaac Newton and Gottfried Leibniz both developed it independently.
Opinion: Calculus is much harder, mostly because of it's complexity. Calculus requires much more formula memorization and ingenuity.
Issac Newton and Gottfried Leibniz invented the calculus and argued the rest of their lives over who had the priority in this invention.
Izac Newton