FP1 - Trig

Hi !
I'm struggling with the questions on some FP1 work I got as we haven't covered any of this in class. I've worked out how to do it all apart from this question:

Express in terms of cos(2pi/5) and Cos(pi/5)

Unparseable latex formula:

Cos(\frac{2\pi}{5})Cos(\frac{\pi}{5}) + Cos(\frac{\pi}{5})Cos(\frac{3\pi}{5}) + Cos(\frac{\pi}{5})Cos(\frac42\pi}{5}) + Cos(\frac{2\pi}{5})Cos(\frac{3\pi}{5})+Cos(\frac{2\pi}{5})Cos(\frac{4\pi}{5})+Cos(\frac{3\pi}{5})Cos(\frac{4\pi}{5})

I have no idea where to even start as all the others were simply simplifying using trig graphs and the cast diagram.
All help appreciated ! Thanks !

Reply 1

A.J.B

Joteca

Hi !
I'm struggling with the questions on some FP1 work I got as we haven't covered any of this in class. I've worked out how to do it all apart from this question:

Express in terms of cos(2pi/5) and Cos(pi/5)

Unparseable latex formula:

Cos(\frac{2\pi}{5})Cos(\frac{\pi}{5}) + Cos(\frac{\pi}{5})Cos(\frac{3\pi}{5}) + Cos(\frac{\pi}{5})Cos(\frac42\pi}{5}) + Cos(\frac{2\pi}{5})Cos(\frac{3\pi}{5})+Cos(\frac{2\pi}{5})Cos(\frac{4\pi}{5})+Cos(\frac{3\pi}{5})Cos(\frac{4\pi}{5})

I have no idea where to even start as all the others were simply simplifying using trig graphs and the cast diagram.
All help appreciated ! Thanks !

sry i cant help, but i need to ask....if u do FP1 on edexcel, and if ur doing it on the 2004 curriculum, where can i get a book and what does it look like?

Reply 2

kcfch

14

consider the double angle formulae

Reply 3

Joteca

OP

kcfch

consider the double angle formulae

We've never done that. I don't even think it's in my formula book, could you tell me what it is please? :smile:

Reply 4

insparato

15

Have you done C1 - C4 ?

Reply 5

kcfch

14

youre doing further maths and you havent covered double angle formulae?! :s-smilie:

its in C3... well anyway, its like this:
cos (A+B) = cosAcosB - sinAsinB
cos (A-B) = coaAcosB + sinAsinB
sin (A+B) = sinAcosB + sinBcosA
sin (A-B) = sinAcosB - sinBcosA

Reply 6

Joteca

OP

I've only done C1 and C2, this year I'm doing C3 C4 FP1-4 and D1 S1 and M2

Thanks ! I should be able to do it now ! :biggrin:

FP1 - Trig

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