# FP1 - quick question!Watch

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#1
You know when you're doing polar coordinates.. does it matter if you specify a point below the x-axis with a negative theta value?

E.g would it be better to put this: (2a, 5pi/3) or is it fine to put this (2a, -pi/3)?
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11 years ago
#2
Yes you do - polar co-ordinates are usually defined from -pi to pi
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#3
Ah okay thanks
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11 years ago
#4
Depends on the question and how they define the curve.The co-ordinates you give must be in the domain of theta for which the curve is defined.I've made that mistake before in the Jan 08 paper admittedly...
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11 years ago
#5
As far as I'm aware on Edexcel, and . Other conventions vary, but on Edexcel that's what they want.
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11 years ago
#6
Yeah.. you look at how it's defined in the question.

So if it says the curve is from 0<x<2pi then you would use 5pi/3

But if it says -pi<x<pi then you would use -pi/3
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11 years ago
#7
(Original post by tommmmmmmmmm)
As far as I'm aware on Edexcel, and . Other conventions vary, but on Edexcel that's what they want.
You cant have both positive and negative pi. I dont think negative pi is included, but yes it can vary.
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11 years ago
#8
(Original post by silent ninja)
You cant have both positive and negative pi. I dont think negative pi is included, but yes it can vary.
Yeah, maybe the second sign should just be .
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11 years ago
#9
You're usually expected to give the principal argument, but in some cases you wouldn't lose marks for not giving the principal. Still better to be safe though.
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11 years ago
#10
Ha, I'm wasting time away on TSR when I have revision exercises and solomon papers to be doing
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#11
Ahhhh makes sense thanks
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11 years ago
#12
Right, my minds gone blank: when you write polar coordinates, does it go or ?
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#13
the first one

just remember it like cartesian equations.. which are usually in the form y=f(x) (i.e. y, then x in order of appearance) and so coordinates are (y,x) and polar equations are usually in the form r=af(theta) (i.e. r then theta) so it's (r, theta)
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11 years ago
#14
Erm, Cartesian coordinates don't go (y, x), they surely go (x, y)?
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11 years ago
#15
*screams*:

(c) Use linear interpolation once between the values x = 1 and x = 1.5 to find an
approximate value for β, giving your answer correct to 1 decimal place.

ARGH!

Enough to put you off FP1 for life.

EDIT: sorry, I thought this was the ultimate thread, so apologies to the OP for spamming it up. But be reet.
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11 years ago
#16
(Original post by tommmmmmmmmm)
*screams*:

(c) Use linear interpolation once between the values x = 1 and x = 1.5 to find an
approximate value for β, giving your answer correct to 1 decimal place.

ARGH!

Enough to put you off FP1 for life.

EDIT: sorry, I thought this was the ultimate thread, so apologies to the OP for spamming it up. But be reet.
Linear interpolation is easy if you can picture it graphically, just draw some triangles!
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11 years ago
#17
Yeah thats like the easiest part of FP1. I would be so happy if one of those comes up.
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#18
Erm, Cartesian coordinates don't go (y, x), they surely go (x, y)?
Oh yeah.. lol :/ I'm very, very tired lol, I blame the utter stupidity on lack of sleep *nods*
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