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# Trig equation watch

1. Solve: 2cos(2x)=1+cos(x)
When 0<x<360
2. (Original post by JoshDes)
Solve: 2cos(2x)=1+cos(x)
When 0<x<360

3. (Original post by DylanJ42)

Protip: whenever you're writing trigonometrical expressions using , put a \ in front of the trig function so that it typesets it correctly instead of writing down the three variables c, o and s mashed together. That is: v/s .
4. (Original post by Zacken)
Protip: whenever you're writing trigonometrical expressions using , put a \ in front of the trig function so that it typesets it correctly instead of writing down the three variables c, o and s mashed together. That is: v/s .
Noted, thank you (soon I will be a latex master)
5. (Original post by DylanJ42)
Noted, thank you (soon I will be a latex master)
You'll be teaching the young 'uns in no time.
6. (Original post by DylanJ42)

How did you get to this?
7. (Original post by Mitul106)
How did you get to this?
***

*** This line can be obtained by expressing as and expanding that

However I could not tell you where = comes from, so that's as far back as I can go

Zacken will probably know
8. (Original post by DylanJ42)
Zacken will probably know
There's an ugly geometric proof and a nicer one, but there's no way I'm writing it up - the person can google it.
9. e^i(x+y)=cos(x+y)+isin(x+y)

(cosx+isinx)(cosy+isiny)=e^ix * e^iy

cos(x+y)+isin(x+y)=(cosx+isinx)( cosy+isiny)

Equate imaginary and real parts.

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Updated: January 31, 2016
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