- ... polar1
- Note that
Equations 8 and 11 require
knowlege of which quadrant the angle lies in, because
ranges
over
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- ... cone2
- double cone means that it is
two ``standard'' cones joined at their apices.
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- ... equation3
- The equation itself is rather
fierce and you would not be expected to do the full expansion in an
exam. For those who are interested, it looks like this:
t4 (
xD4
+ yD4
+ zD4
+ 2 xD2 yD2
+ 2 xD2 zD2
+ 2 yD2 zD2
)
+ t3 (
4 xD3 xE
+ 4 yD3 yE
+ 4 zD3 zE
+ 4 xD2 yD yE
+ 4 xD2 zD zE
+ 4 xD xE yD2
+ 4 yD2 zD zE
+ 4 xD xE zD2
+ 4 yD yE zD2
)
+ t2 (
- 2 R2 xD2
- 2 R2 yD2
+ 2 R2 zD2
- 2 r2 xD2
- 2 r2 yD2
- 2 r2 zD2
+ 6 xD2 xE2
+ 2 xE2 yD2
+ 8 xD xE yD yE
+ 2 xD2 yE2
+ 6 yD2 yE2
+ 2 xE2 zD2
+ 2 yE2 zD2
+ 8 xD xE zD zE
+ 8 yD yE zD zE
+ 2 xD2 zE2
+ 2 yD2 zE2
+ 6 zD2 zE2
)
+ t (
- 4 R2 xD xE
- 4 R2 yD yE
+ 4 R2 zD zE
- 4 r2 xD xE
- 4 r2 yD yE
- 4 r2 zD zE
+ 4 xD xE3
+ 4 xE2 yD yE
+ 4 xD xE yE2
+ 4 yD yE3
+ 4 xE2 zD zE
+ 4 yE2 zD zE
+ 4 xD xE zE2
+ 4 yD yE zE2
+ 4 zD zE3
)
+ (
R4
- 2 R2 xE2
- 2 R2 yE2
+ 2 R2 zE2
+ r4
- 2 r2 R2
- 2 r2 xE2
- 2 r2 yE2
- 2 r2 zE2
+ xE4
+ yE4
+ zE4
+ 2 xE2 yE2
+ 2 xE2 zE2
+ 2 yE2 zE2
)
= 0
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- ...
defined4
- The disc is also arbitrarily defined if you want a
circular disc, but it could be transformed to provide an
ellipse.
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- ...
definition5
- The sphere has unit radius; the cylinder has unit
radius and is aligned with the z-axis; the cone is similarly aligned
and has unit slope; the torus is aligned with the z-axis.
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- ... transformation6
- Where
is a translation,
a rotation, and
a scaling.
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- ... where7
- If you are wondering where
r has disappeared to, remember that, in a unit sphere, r=1.
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- ... being8
- If you try this at home
you will find that you will need to divide through by the factor
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- ...
doubles9
- It doesn't quite double the number of points when the
sequence is open and of finite length, but we will gloss over that at
the moment.
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