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**Daniel123****Member**- Registered: 2007-05-23
- Posts: 663

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I've done the first part using induction. The polynomials I chose were:

However, the last part is a bit tricky.

I can't see how to write this in the form

though. I know that andCan anyone help? (Small hints preferred) Thanks.

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**Daniel123****Member**- Registered: 2007-05-23
- Posts: 663

No one?

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**Kurre****Member**- Registered: 2006-07-18
- Posts: 280

Cos2x+Cos3x=0

Cos2x=-Cos3x

Cos2x=Cos(pi-3x)

1)2x=3x-pi->x=pi->cosx=-1

2)2x=pi-3x->x=pi/5

looks like something is wrong with your equation...

*Last edited by Kurre (2008-12-06 07:14:54)*

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**Daniel123****Member**- Registered: 2007-05-23
- Posts: 663

Kurre wrote:

Cos2x+Cos3x=0

Cos2x=-Cos3x

Cos2x=Cos(pi-3x)

1)2x=3x-pi->x=pi->cosx=-1

2)2x=pi-3x->x=pi/5

looks like something is wrong with your equation...

You're right.

I'm actually rather stupid.

The factor should be (x+1), in which case x = -1 does work, as we can let x = cosθ (which we have to do anyway). Also,

Thanks

The point of the question was obviously to work in the trigonometric form, as the value of phi s.t

isn't obvious.*Last edited by Daniel123 (2008-12-06 08:20:13)*

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