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Excel input for 7671 calculation

lyledunn

Could any one assist this old duffer? I have successfully put together a fairly comprehensive circuit calculation spreadsheet in Excel for circuits up to and including 16mm2. However, can anyone advise how I can enter a cell instruction to convert Cos theta to the sine of the angle. For example power factor is 0.8 and sine of same angle is 0.6. All I want to do is enter 0.8 into a cell and the corresponding cell correctly inputs 0.6. 

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  • 0

    Not at desk but think

    =sqrt(1-PF^2)

    (Where PF is the cell containing cos(th))

    will do the trick.

    Note that excel’s trig functions take radians as their inputs, just to catch you out (c;

    So to get the phase angle from PF=cos(th), you need =degrees(acos(PF))

    **Edited to correct formula!**

  • 0 in reply to Jam

    Ps should have said first that the reverse for PF from phase angle is =cos(radians(th))

  • 0 in reply to Jam

    Whoops, forgot a square root there. Edited.

  • 0 in reply to Jam
    Jam said:
    =sqrt(1-PF^2)

    DEFINITELY - mathematicians use the following identity to remember it by:

    sin2θ + cos2θ = 1

    As Mike says, it falls straight out of Pythagoras. If we have A as the side of a right-angled triangle adjacent to the angle θ, B as the side opposite, and H as the hypotenuse, then according to Pythagoras (I'm sure someone will correct me that this ought to be the 47th Proposition of Euclid though), we have:

    A2 + B2 = H2

    Dividing both sides by H2, we have:

    (A/H)2 + (B/H)2 = 1 ... and if we remember that A/H is defined as cosθ, and B/H is defined as sinθ, the mathematical identity pops out.

  • 0 in reply to gkenyon

    Thanks Graham and Jam, works a treat!

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