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FP1 question

So I started doing FP1 and I'm confused..



Why isn't the argument of z, (pi + alpha) , in the first picture?

As for the 2nd pic, why isn't the argument of z, (2pi - alpha) ?
Reply 1
Avatar for Jam'
Jam'
15
We normally use this thing called the principal argument, such that all arguments are within
Unparseable latex formula:

-\pi \textless arg(z) \leq \pi



Can you see why these values have been used now? You're technically correct in your thinking and the angles are accurate; it's just something of a convention.
(edited 11 years ago)
Reply 2
Avatar for Llewellyn
Llewellyn
14
The argument could be what you suggest or what is posted. The argument of z is simply the angle from the positive x axis. You could say an argument is pi/2, or you could say an argument is -3pi/2, because that would give you the same angle.

I have been taught to do it your way, and have a positive angle between 0 and 2pi. However, the approach shown is not incorrect.

It's pretty much just a matter of style or a convention. Like (sinx)^2 is normally written as sin^2 (x). Neither is wrong, and they both mean exactly the same thing, but one is simply more common.
(edited 11 years ago)
Reply 3
Avatar for TDL
TDL
2
Original post by sabre2th1
So I started doing FP1 and I'm confused..



Why isn't the argument of z, (pi + alpha) , in the first picture?

As for the 2nd pic, why isn't the argument of z, (2pi - alpha) ?


−π<θ≤π -\pi<\theta\leq\pi

Take a look at page 15.
Reply 4
Avatar for Jam'
Jam'
15
In exams they usually want you to give the principal argument, so get into the habit of producing this.
Reply 5
Avatar for Llewellyn
Llewellyn
14
Original post by Jam'
In exams they usually want you to give the principal argument, so get into the habit of producing this.

What board are you on? (or were you on?)
Reply 6
Avatar for Jam'
Jam'
15
Original post by Llewellyn
What board are you on? (or were you on?)


OCR:MEI - bane of my life lol
Reply 7
Avatar for Blazy
Blazy
8
Original post by Jam'
OCR:MEI - bane of my life lol


But we have a Differential Equations module :biggrin:!
Reply 8
Avatar for Jam'
Jam'
15
Original post by Blazy
But we have a Differential Equations module :biggrin:!


I wanted to do that. It looked interesting, but my school didn't teach it and I did FM in a year alongside A2 Maths, so I stuck to the familiar Mech and Stats modules - wasn't prepared to do heroics lol.

Have you just finished AS or A2?
Reply 9
Avatar for sabre2th1
sabre2th1
OP
12
Original post by Jam'
We normally use this thing called the principal argument, such that all arguments are within
Unparseable latex formula:

-\pi \textless arg(z) \leq \pi



Can you see why these values have been used now? You're technically correct in your thinking and the angles are accurate; it's just something of a convention.



Original post by Llewellyn
The argument could be what you suggest or what is posted. The argument of z is simply the angle from the positive x axis. You could say an argument is pi/2, or you could say an argument is -3pi/2, because that would give you the same angle.

I have been taught to do it your way, and have a positive angle between 0 and 2pi. However, the approach shown is not incorrect.

It's pretty much just a matter of style or a convention. Like (sinx)^2 is normally written as sin^2 (x). Neither is wrong, and they both mean exactly the same thing, but one is simply more common.



Original post by TDL
−π<θ≤π -\pi<\theta\leq\pi

Take a look at page 15.


Thanks, I understand :smile:

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