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Author Topic: TRIG HELP D:  (Read 1754 times)  Share 

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ninbam1k

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TRIG HELP D:
« on: November 28, 2010, 01:00:14 pm »
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heyy guys, how do i simply this? been trying to figure this out for agess :(

(1 + sin2x + cos2x)/(1 + sin2x - cos2x)

HELP  :-[
« Last Edit: November 28, 2010, 01:06:55 pm by ninbam1k »

pi

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Re: TRIG HELP D:
« Reply #1 on: November 28, 2010, 01:03:49 pm »
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1 + 2sin2x

= 1 + 4 sinx cosx


(or was there supposed to be brackets on the denominator?)

ninbam1k

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Re: TRIG HELP D:
« Reply #2 on: November 28, 2010, 01:06:35 pm »
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my bad
brackets on the denominator
so the whole top on the whole bottom

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Re: TRIG HELP D:
« Reply #3 on: November 28, 2010, 01:09:54 pm »
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It's a matter of simplifying the top and bottom into a product of factors so that you can later cancel out.



Extra hint 1:
The 1s on the top and bottom stick out... can you expand one of the sin(2x) or cos(2x)s to get rid of them?


Extra hint 2:
You have (2x)'s and (x)'s as angles, but it's better to make them all the same. So expand the rest of the (2x)'s.




pi

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Re: TRIG HELP D:
« Reply #4 on: November 28, 2010, 01:21:50 pm »
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I only got this far:

(sin^2 x + cos^2 x + 2 sinx cox - sin^2 x + cos^2)/(sin^2 x + cos^2 x + 2 sinx cox + sin^2 x - cos^2)

= (2 cos^2 x + 2 sinx cosx)/(2 sin^2 x + 2 sinx cosx)

= (2 cosx (cosx+ sinx))/(2 sinx (cosx+ sinx))

= 2 cotx (cosx + sinx)/(sinx + cosx)

= 2 cotx


Is this right? Now it is right!



(I REALLY need to learn LaTeX these hols!)
« Last Edit: November 28, 2010, 01:28:07 pm by Rohitpi »

ninbam1k

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Re: TRIG HELP D:
« Reply #5 on: November 28, 2010, 01:22:22 pm »
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wooo i got it :D thanks alot guys :}

pi

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Re: TRIG HELP D:
« Reply #6 on: November 28, 2010, 01:25:19 pm »
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wooo i got it :D thanks alot guys :}

What the answer? I think I might have been wrong...

ninbam1k

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Re: TRIG HELP D:
« Reply #7 on: November 28, 2010, 01:25:38 pm »
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i got cotx buddy

(1+ sin2x + cos2x) / (1+sin2x-cos2x)

= (2(cosx)^2 + 2sinxcosx) / (2(sinx)^2 +2sinxcosx)

kinda skipped a step here but all i did was let cos2x = 2(cosx)^2 - 1 for the numerator and cos2x = 1 - (sinx)^2 for the denominator

FACTORISE

= (2cosx)(cosx + sinx) / (2sinx)(sinx + cosx)

CANCEL OUT (sinx+cosx)

= 2cosx / 2 sinx

= cotx :}
« Last Edit: November 28, 2010, 01:27:33 pm by ninbam1k »

xZero

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Re: TRIG HELP D:
« Reply #8 on: November 28, 2010, 01:26:43 pm »
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@Rohitpi the 2 cancles out so its cot x
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pi

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Re: TRIG HELP D:
« Reply #9 on: November 28, 2010, 01:27:24 pm »
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lol, forgot to cancel the 2  :idiot2:

Yep, you are right!

TrueTears

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Re: TRIG HELP D:
« Reply #10 on: November 29, 2010, 02:14:43 am »
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i got cotx buddy

(1+ sin2x + cos2x) / (1+sin2x-cos2x)

= (2(cosx)^2 + 2sinxcosx) / (2(sinx)^2 +2sinxcosx)

kinda skipped a step here but all i did was let cos2x = 2(cosx)^2 - 1 for the numerator and cos2x = 1 - (sinx)^2 for the denominator

FACTORISE

= (2cosx)(cosx + sinx) / (2sinx)(sinx + cosx)

CANCEL OUT (sinx+cosx)

= 2cosx / 2 sinx

= cotx :}

another way, i haven't checked it all but try multiplying by [1-(sin2x -cos2x)]/[1-(sin2x-cos2x)], this way is definitely longer but it's just for fun haha

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