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Question about Casio fx-115MS

Discussion in 'Electronic Basics' started by Jack Crane, Nov 25, 2004.

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  1. Jack Crane

    Jack Crane Guest

    OK, Robert, you got me. Twice I've entered thru SHIFT SOLVE and the first
    prompt is "B?"; and I'm not given a chance to enter A. Does this really
    work?

    Tried a simpler equation, A-squared = B X C-squared, with A=8, C=2. Same
    thing happened.

    Jack
     
  2. Solve uses an iterative solver to try to figure out a numerical
    solution. Say you want to figure out the right resistor value to make
    divider, but you were too lazy to do the algebra in your head. If your
    input voltage was 10 volts, and you wanted 1.7 volts out, you could type

    1.7 alpha = 10 * alpha A / ( alpha A + alpha B) shift solve

    You then get a prompt for A, as in "A? ". Say you want to solve for A.
    Then, hit the down key (the bottom of the circular key). You get a "B?"
    prompt. Enter a value for B. (say you have a 10k resistor)

    10000 =

    then get back to the A? prompt by typing up arrow (the top of the
    circular key) and type

    shift solve

    it'll crank for a bit, then display A= on the first line, and 2.048...k
    on the second line. Thus, for a value of B=10k, a value of A=2.05k will
    get you 1.7V.

    The trick is to use the up and down key to enter values for variables
    you have values for, and then use shift solve on the one you want the
    value for.

    --
    Regards,
    Robert Monsen

    "Your Highness, I have no need of this hypothesis."
    - Pierre Laplace (1749-1827), to Napoleon,
    on why his works on celestial mechanics make no mention of God.
     
  3. Jack Crane

    Jack Crane Guest

    Did this twice and both times with A= on the first line, the second line
    was 0.

    Thus, for a value of B=10k, a value of A=2.05k will
    Tried a really simple equation, 3 = A*B (3 Alpha = Alpha A * Alpha B),
    with B=3. Again, with A= showing on first line, second line showed 0.

    Jack
     
  4. Again, you switch to B using the 'down' key, which is the bottom of the
    circular key. Enter the values for the unknowns you want, and then
    select the one you want to solve for. enter 'shift solve' and it will
    solve the equation if it can do it using iteration.

    --
    Regards,
    Robert Monsen

    "Your Highness, I have no need of this hypothesis."
    - Pierre Laplace (1749-1827), to Napoleon,
    on why his works on celestial mechanics make no mention of God.
     
  5. Jack Crane

    Jack Crane Guest

    Am I wrong to expect the calculator to solve "3=A*B" for A, given B = 3?
    I believe I did exactly what you said to do. I'll spell out completely
    the keys I pushed : 3, ALPHA, =, ALPHA, A, *, ALPHA, B, SHIFT, SOLVE,
    down-arrow, 3, =, up-arrow, SHIFT, SOLVE. At this point the top line
    shows A=; the bottom line shows 0. (by * I mean the multiplication key,
    "X").

    Thanks for being so patient with me.

    Jack
     
  6. No, it works for me.
    Make sure you are in 'comp' mode, not 'cmplx' mode. The solve function
    does not work in complex mode. Enter 'mode clr' and then '1' to enter
    'comp' mode.

    --
    Regards,
    Robert Monsen

    "Your Highness, I have no need of this hypothesis."
    - Pierre Laplace (1749-1827), to Napoleon,
    on why his works on celestial mechanics make no mention of God.
     
  7. Jack Crane

    Jack Crane Guest

    Yes, I've been in comp mode.

    Jack
     
  8. After entering your formula for 3=A*B, can you switch between "A=" and
    "B=" on the top display line using up and down arrow?

    --
    Regards,
    Robert Monsen

    "Your Highness, I have no need of this hypothesis."
    - Pierre Laplace (1749-1827), to Napoleon,
    on why his works on celestial mechanics make no mention of God.
     
  9. Jack Crane

    Jack Crane Guest

    No. After "A=" appears, up-arrow produces "3", and I'm stuck there.
    Down-arrow doesn't work after "A=" appears.

    Jack
     
  10. Look at the calculator. There is a big round button right underneath the
    center of the display. The up and down buttons are on the top and bottom
    of that. Is that what you are pushing? If not, then that's your problem.
    If so, then your calculator is broken.

    --
    Regards,
    Robert Monsen

    "Your Highness, I have no need of this hypothesis."
    - Pierre Laplace (1749-1827), to Napoleon,
    on why his works on celestial mechanics make no mention of God.
     
  11. Jack Crane

    Jack Crane Guest

    Yes, that's what I'm pushing.

    Thanks,

    Jack
     
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