You're already an old hand at using functions in Maple. But you might be surprised to realize that you already know how to use functions in your C programs, too! Think back to the homework for the previous lesson, in which you found the positions of a squatter's joints. What functions did you use then?
When you give values to a function and get back a result value, we say that you have invoked or called the function. The values that you give to the function are called arguments. Consider the following C statement:
x2 = x1 + cos(theta);
That statement contains an invocation of the built-in cos function. The value of the variable theta is the argument to the cos function.