Why the variable remains undefined?

[RWickrama]

I defined a user-defined function: However the variable after the equal remain undefined.

Already I created similar functions. But, this one is giving me a hard time. Could someone help me please.

MathCAD Prime 4.0

[ValeryOchkov]

Do not use = operatorat the end of a function creating!

[Fred_Kohlhepp]

If you define w and AB above your function it will evaluate using those value.  As Val demonstrated, using the function with other values will evaluate with those values.

[VladimirN]

Something like this?