Usually you memorize a number of rules, or look them up in tables - for example, rules for the derivative of powers, trigonometric functions, addition, multiplication, etc. - and apply them to specific cases. This includes applying the "chain rule", for more complicated expressions. For a quick overview, read the Wikipedia article on "Derivative". For more details, read an introductory book on Calculus.
Sir Isaac Newton and Leibniz.
You don't normally calculate derivatives with a calculator. Please clarify what calculation you were trying to do.
Calculus (or, some advanced pre-calculus classes).
Are you asking a math question or a business question? Why are you asking it in the "relationships" area?
Math.
you should just know about... -Trigonometric Identities-Logarithms, and Natural Logs-Limits-Derivatives
To calculate money spent, to make percentages on a pie chart, solve math problems, add fractions, and calculate trajectories.
yes, they use math to calculate the area for the room.
"key concept" is not a mathematical term . A key concept is an important idea. Two key concepts in math are derivatives and integrals of functions. ( "function" is also a key concept.)
Most people rarely sit down and think that they are calculating derivatives, however derivatives are used in almost every process that we do. Simple driving uses derivatives to calculate speed. Computers use derivatives for a lot of signal processing algorithms. The stock market uses derivatives to see if a stock how stocks are changing. Anything that relates two values at different times most likely uses a derivative process.
To calculate your taxes.
That basically means to calculate.