Sometimes when I evaluate a derivative symbolically in mathcad of a certain function, it gives me 0 when its not

[prajendran]

Sometimes when I evaluate a derivative symbolically in mathcad of a certain function, it gives me 0 when its not. can anyone help?

[Fred_Kohlhepp]

Separate out the function, and it will evaluate.  Don't know why your sheet fails.

[RichardJ]

It's a problem with labels. You have two occurrences of phi with different labels, so Mathcad views them as different. It's equivalent to d/dA(f(B)), which is of course zero. Set the labels to both be "variable" and it works

In Mathcad Prime you have to be careful with labels!

It would have been better to continue the previous thread rather than starting a new one.

[prajendran]

I couldn't attach a new file in the reply.... so i had 2 start a new one....

[prajendran]

I dont know where I had phi as different labels?