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    Hi, I'm not sure at all what Q1 is telling me to do. What does 'combine these expressions' mean?

    Fp= fx*sin(theta)*cos(psi) + fy*sin(theta)*sin(psi) + fz*cos(theta)
    F(theta)= p(fx*cos(theta)*cos(psi) + fy*cos(theta)*sin(psi) - fz*sin(theta)
    F(psi)= (p*sin(theta)) (-fx*sin(psi) + fy*cos(psi))

    n.b. The p is supposed to be rho.
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    (Original post by jordanwu)
    Hi, I'm not sure at all what Q1 is telling me to do. What does 'combine these expressions' mean?

    Fp= fx*sin(theta)*cos(psi) + fy*sin(theta)*sin(psi) + fz*cos(theta)
    F(theta)= p(fx*cos(theta)*cos(psi) + fy*cos(theta)*sin(psi) - fz*sin(theta)
    F(psi)= (p*sin(theta)) (-fx*sin(psi) + fy*cos(psi))

    n.b. The p is supposed to be rho.
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    (Original post by jordanwu)
    Hi, I'm not sure at all what Q1 is telling me to do. What does 'combine these expressions' mean?
    Solve for f_x, f_y, f_z in terms of F_\rho, F_\theta, F_\psi
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    (Original post by DFranklin)
    Solve for f_x, f_y, f_z in terms of F_\rho, F_\theta, F_\psi
    Isn't that kind of repeating the question? I can't figure out whether to add all of the expressions or do something with them separately
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    (Original post by jordanwu)
    Isn't that kind of repeating the question? I can't figure out whether to add all of the expressions or do something with them separately
    You need to find expressions for f_x, f_y, f_z in terms of F_\rho, F_\theta, F_\psi.

    To do a much simpler example, if you'd found

    F_\rho = F_x + 2F_y
    F_\theta = F_x - F_y
    F_\phi = F_z,

    Then you could, subtract the 2nd equation from the 1st to get F_\rho-F_\theta = 3F_y and thus F_y = \frac{1}{3}(F_\rho-F_\theta)

    Similarly, adding twice the 2nd equation to the 1st gives you F_x = \frac{1}{3}(F_\rho + 2 F_\theta)

    And finally of course F_z = F_\phi.

    Your problem is somewhat more complicated, of course.
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    (Original post by DFranklin)
    You need to find expressions for f_x, f_y, f_z in terms of F_\rho, F_\theta, F_\psi.

    To do a much simpler example, if you'd found

    F_\rho = F_x + 2F_y
    F_\theta = F_x - F_y
    F_\phi = F_z,

    Then you could, subtract the 2nd equation from the 1st to get F_\rho-F_\theta = 3F_y and thus F_y = \frac{1}{3}(F_\rho-F_\theta)

    Similarly, adding twice the 2nd equation to the 1st gives you F_x = \frac{1}{3}(F_\rho + 2 F_\theta)

    And finally of course F_z = F_\phi.

    Your problem is somewhat more complicated, of course.
    Okay I somewhat get the idea now, thanks
 
 
 
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