When you define a function, Mathcad does not try to evaluate it until you use it later on in the worksheet. If there is an error, the use of the function is marked in error, even though the real problem may be in the definition of the function itself. Figure 7-14 shows two examples of this.When a user-defined function is marked in error, be sure to check the function definition to find the actual source of error. Note that the second example in shows a recursive definition generating a “stack overflow” error message. Although Mathcad supports recursive function definitions, as described in “Recursive function definitions” on page 136, you must supply an initial condition in your function definition that prevents the recursion from going on forever.