IF statement with IS BLANK and multiple conditions

Hi there,
New to the board and have a beginner question.

Right now I have a formula that looks like this:

=IF(ISBLANK(E12), ((SQRT(((1/F12)^2)-1))*N12), ((SQRT(((1/E12)^2)-1))*N12))It works fine, except I want to add in a condition that if neither E12 of F12 have a value, show a vlue of "0.00"

Have a couple of other formulas in the same spreadsheet that I would like to apply the same logic too. My understanding is that I can do this by adding an "OR" statement but am not well versed in Excel.

Another formula that i'm working on is as follows:

=IF(ISBLANK(G12), D12*F12*L12*M12, D12*G12*L12*M12)
If F and G are both blank use the value in cell "E12"

Hopefully this will clarify what I am trying to do. (I posted this in a reply below as well).

For the first formula:

Here is the math: ((SQRT(((1/E12)^2)-1))*N12)
Condition 1: If E12 is blank, use the value in F12.
So the formula looks like this: =IF(ISBLANK(E12), ((SQRT(((1/F12)^2)-1))*N12), ((SQRT(((1/E12)^2)-1))*N12))
New condition to be added: If E12 and F12 do not contain a value, show a "0.00"

For the 2nd formula, the math is as simple as this: D12*G12*L12*M12
Condition 1: If G12 is blank, use the value in F12
Hence the formula: =IF(ISBLANK(G12), D12*F12*L12*M12, D12*G12*L12*M12)
New condition to be added: If both G12 AND F12 are blank, use the value in E12.


Any help is appreciated.

Thanks!