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# Spherical coordinates watch

1. 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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2. (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.
bump
3. (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 in terms of
4. (Original post by DFranklin)
Solve for in terms of
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
5. (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 in terms of .

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

,

Then you could, subtract the 2nd equation from the 1st to get and thus

Similarly, adding twice the 2nd equation to the 1st gives you

And finally of course .

Your problem is somewhat more complicated, of course.
6. (Original post by DFranklin)
You need to find expressions for in terms of .

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

,

Then you could, subtract the 2nd equation from the 1st to get and thus

Similarly, adding twice the 2nd equation to the 1st gives you

And finally of course .

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

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