Use error tracing to detect the original source of calculation errors. When a worksheet contains an expression that is dependent on one or more definitions made earlier in the worksheet, an error in that expression can be traced to an earlier definition. Consider the following example:

When you click outside the math region, PTC Mathcad flags any errors by placing a red circle around the erroneous expression.

The error appears in g(0). However, g(0) is based on the definition of f(x). In this case, you cannot divide by zero, so f(x) is causing an error to appear. You can click inside the region that contains the red borderline to view the relevant error message.