Hi!

I begin to do math in Excel (2002), but at beginning stuck with luck of
knowledge, can anybody help me?

Simple formulas:

I want to calculate frequency given by formula: f=1/(2*pi*sqrt(L*C)),
where f=frequency, L=inductance, C=capacitance.

L is in cell A1,
C is in cell A2,
f is in cell A3

In cell A7, I put the formula:
[cell A7] =1/(2*PI()*SQRT(A1*A2))

The formula use only A1 and A2 value for calculating. This works,
because inductance and capacitance are known. In A7 it give me result.

But, what if I know only frequency, and capacitance, and want to know
(calculate) which inductance to use?

In cell A5 I wrote the formula:
[cell A5] =1/((2*PI())^2)*A3^2*A2)

The formula now use only A2 and A3 and put result in A5. This works as well.

Now, I want to know the capacitance from A1, and A3 and result is in A6:
[cell A6] =1/((2*PI())^2*A3^2*A1)
---

The problem:

How to write input in A1, A2 and A3 so that if one field is empty (for
example A1) not give me result in A5 and A6: [#DIV/0!] ?

When given result in cell A5 manually Copy/PasteSpecial (because
Copy/Paste "transfer" formula instead value) to A1, only then I get
right results in A6 and A7.

Is possible to do it automatically?

I can in cell A1 put =A5, but next time when I want to calculate
capacitance vs. frequency to give inductance, I need to write in field
A1 and A3 values - this attempt overwrite =A5, and then all results in
formulas A5, A6, and A7 are incorrect because in A2 is an "old" value.


What to do?

How to make each three calculation "independent", so that every time it
can calculate from only two inputs without errors?

And, how to "lock" formulas, so that not permit me accidentally
overwrite cells consisting formulas with some number?

Thank you in advance,

Milan Karakas