The answer depends on when "back then" was. But since you have not bothered to share that crucial bit of information, I cannot provide a more useful answer.
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
It is certainly used in calculus, just as calculus can be used in trigonometry.
Mainly Leibniz's and Newton's version is used in Calculus Textbooks.
Calculus can be traced back to the Egyptian Moscow papyrus (c. 1820 B.C.).
The difference between Leibniz calculus to Newton calculus was that Leibniz developed Newton's calculus into the calculus we all know today. For instance, diffentiation and intergration, limits, continuity, etc. This type of calculus was the pure mathematics. On the otherhand, the calculus which Newton found was that used in physics, such as speed and velocity which helped with physics greatly. Today, calculus not only used in just mathematics or physics, but used in finance, as well as exploited in engineering.
Get Mad back at them
In the 'real world', the purpose of a course of study in pre-calculus is to prepare the student for a course of study in Calculus.
In the 'real world', the purpose of a course of study in pre-calculus is to prepare the student for a course of study in Calculus.
For Literally Everything.
yes it is
pi = 3.14. It is an important and often used metric dating back hundreds of years in algebra and calculus.
Calculus was created to prove physics which defines the laws of nature.