Lil maths help please.

Mason-

Mason-

Mason-

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Okay got the following:

w denotes the complex number cos (2/5)pi + isin (2/5)pi

express w^2 w^3 and w* in polar form, with arguments in the interval 0<= Theta < 2pi

so w^2 = cos (4/5)pi + isin (4/5)pi
w^3 = cos (6/5)pi + isin (6/5)pi

but what the hell is w*

any help please :)
 
For the complex conjugate, just negate the argument; in this case, arg(w*) = -(2/5)*pi. Also, polar form means it should be expressed as an exponential:

w = exp((2/5)*pi*i)
w² = exp((4/5)*pi*i)
w³ = exp((6/5)*pi*i)
w* = exp(-(2/5)*pi*i).
 
Last edited:
Inquisitor said:
For the complex conjugate, just negate the argument; in this case, arg(w) = -2pi/5. Also, polar form means it should be expressed as an exponential; e.g. w = exp((2/5)*pi*i).
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Complex conjugate, how amateur of me ffs, how did I forget that.

And no polar form is r(cos(theta) + i sin(theta))
 
Mason- said:
And no polar form is r(cos(theta) + i sin(theta))
Click to expand...

Fair enough. The exponential expression is far more concise, though, and it's generally the preferred notation for complex numbers, at least in most applications :)

Also, remember to normalize the argument of w* :)
 
To be honest if you're going to express a complex number in terms of a magnitude and argument, there's no reason to use the trig form when you can use the exponential form. Depends what your course expects of you though, I guess!
 
Mason- said:
one week of half term and I forget stuff so easy that I was nailing in class. So annoying. Gonna fail these A-Levels fo sho.
Click to expand...
Are you doing the whole 18 modules?

Maths just escapes out of the back of my head if I don't keep a careful watch on it night and day... Quite frustrating.
 
Last edited:
Inquisitor said:
To be honest if you're going to express a complex number in terms of a magnitude and argument, there's no reason to use the trig form when you can use the exponential form. Depends what your course expects of you though, I guess!
Click to expand...

The question starts off with:

3. In this question, w denotes the complex number cos 2/5 pi + i sin 2/5 pi

Just as if a question asked me to work out an angle by using some trig Identity and was using radians, I wouldn't give the answer in degrees if you catch my logic?
 
GreatAuk said:
Are you doing the whole 18? modules?

Maths just escapes out of the back of my head if I don't keep a careful watch on it night and day... Quite frustrating.
Click to expand...

No, doing 12 modules all together over 2 years, they are as follows:

Year 1 I did: C1 C2 M1 S1 D1 FP1
Year 2 I am doing: C3 C4 (Already taken these exams in january) M2 S2 FP2 FP3
 
Mason- said:
Nope FP3, FP2 has stuff like newton-raphson and **** like that in it.
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I did Newton-Raphson in FP1 with Edexcel this January, which board are you on?
EDIT, also edited out my 'FP2?' when I saw a post above.
Mason- said:
No, doing 12 modules all together over 2 years, they are as follows:

Year 1 I did: C1 C2 M1 S1 D1 FP1
Year 2 I am doing: C3 C4 (Already taken these exams in january) M2 S2 FP2 FP3
Click to expand...

Ah, the hard man Further maths route ;)

I've done (C1 C2 C3 C4 S1 M1) (FP1 D1 S2), and I'm doing (FP2 M2 M3)

FP3 looks quite interesting, but I'm finding FP2 plenty challenging enough, so I'm glad to miss that one :)
 
I'm on OCR so we have different things.

FP1 for me consisted of:

Complex numbers
- z = x + iy
- argand diagrams
- Loci
Proof by Induction

and other things that I can't remember lol.
 
Last edited:
Inquisitor said:
For the complex conjugate, just negate the argument; in this case, arg(w) = -(2/5)*pi. Also, polar form means it should be expressed as an exponential:

w = exp((2/5)*pi*i)
w² = exp((4/5)*pi*i)
w³ = exp((6/5)*pi*i)
w* = exp(-(2/5)*pi*i).
Click to expand...

I'm sorry but I thought this was an English speaking forum.
 
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