I'm trying to calculate prism to cut with these formulas but they need a certain sign convention.

P

P

P

x = horizontal decentration

y = vertical decentration

Can anyone break down the sign convention used. It's a little counter-intuitive to me.

Thanks,

Rob

P.S. This is not homework

P

_{V}=x*Sphere + Cylinder*sin(Φ)*(x*sin(Φ) + y*cos(Φ))P

_{H}=y*Sphere + Cylinder*cos(Φ)*(x*sin(Φ) + y*cos(Φ))P

_{r}=sqrt(P_{v}^2 + P_{H}^2)x = horizontal decentration

y = vertical decentration

Can anyone break down the sign convention used. It's a little counter-intuitive to me.

Thanks,

Rob

P.S. This is not homework

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