# parameterization of a semicircle, clarification

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#1
The component of a (clockwise) semicircle and circle with radius 2 are the same, (2cos(t),2sin(t)). Is this because the semicircle is only defined in 0<= y <=2?
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1 month ago
#2
(Original post by localmemelord)
The component of a (clockwise) semicircle and circle with radius 2 are the same, (2cos(t),2sin(t)). Is this because the semicircle is only defined in 0<= y <=2?
It will be on a limited range of t, not necessarily starting at 0. Any arc of the circle can be specified with a limited range.
Last edited by RogerOxon; 1 month ago
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#3
(Original post by RogerOxon)
It will be on a limited range of t, not necessarily starting at 0. Any arc of the circle can be specified with a limited range.
oh ok, so the range would be 0<= t <= pi/2, right?
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1 month ago
#4
(Original post by localmemelord)
oh ok, so the range would be 0<= t <= pi/2, right?
No. t would need to vary by more than that. Can you see why?
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#5
(Original post by RogerOxon)
No. t would need to vary by more than that. Can you see why?
would that range only define a half of the semicircle, i.e. top right of the circle that is centred around the origin?
Last edited by localmemelord; 1 month ago
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1 month ago
#6
(Original post by localmemelord)
would that range only define a half of the semicircle, i.e. top right of the circle that is centred around the origin?
Yes.
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1 month ago
#7
(Original post by localmemelord)
would that range only define a half of the semicircle, i.e. top right of the circle that is centred around the origin?
Yes. It's also the range of t that is important, not where it starts.
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