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April 17, 2024, 06:15:37 am
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Author Topic: how the eff do i teach myself trig in an hour  (Read 5818 times)  Share 

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kido_1

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how the eff do i teach myself trig in an hour
« Reply #15 on: November 08, 2007, 05:26:51 pm »
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I would use the identity:

(cos x) squared = 1- (sinx) squared.

Then let u/A = sinx

Then make it a quadratic..
Then solve.
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reg

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how the eff do i teach myself trig in an hour
« Reply #16 on: November 08, 2007, 05:28:18 pm »
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o.o are trig identities gonna be on exam 1?
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Fitness

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how the eff do i teach myself trig in an hour
« Reply #17 on: November 08, 2007, 05:28:50 pm »
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Quote from: "kido_1"
I would use the identity:

(cos x) squared = 1- (sinx) squared.

Then let u/A = sinx

Then make it a quadratic..
Then solve.


b^2 - 4ac < 0 so you can't.

Originally tried that and how i got my answer before. but realised my mistake and now with that i find there are no real solutions for x  :?
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kido_1

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how the eff do i teach myself trig in an hour
« Reply #18 on: November 08, 2007, 05:35:38 pm »
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Are you sure. Try it again. That is what i did, exactly and I got:

x= pi/6
x=5pi/6
x=3pi/2
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Fitness

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how the eff do i teach myself trig in an hour
« Reply #19 on: November 08, 2007, 05:40:33 pm »
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Quote from: "kido_1"
Are you sure. Try it again. That is what i did, exactly and I got:

x= pi/6
x=5pi/6
x=3pi/2


Yup mistake wit the 4ac. Same answer as you.
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melanie.dee

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how the eff do i teach myself trig in an hour
« Reply #20 on: November 08, 2007, 05:41:40 pm »
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gar does someone want to post their working out, i couldnt do it :(
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Toothpaste

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how the eff do i teach myself trig in an hour
« Reply #21 on: November 08, 2007, 05:50:53 pm »
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(cosx)^2 + (sinx)^2 = 1
=> (cosx)^2 = 1 - (sinx)^2

We have 1+sinx = 2(cosx)^2

1 + sinx = 2[1 - (sinx)^2]
1 + sinx = 2 - 2(sinx)^2]
sinx = 1 - 2(sinx)^2
reorganise:
2(sinx)^2 + sinx - 1

let A = sinx

2A^2 + A - 1
(A+1)(2A-1) = 0

A = -1 or A =0.5

sinx = -1 over the given domain
x = 3pi/2

sinx = 0.5
x = pi/6
and x = 5pi/6
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Fitness

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how the eff do i teach myself trig in an hour
« Reply #22 on: November 08, 2007, 05:52:56 pm »
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Quote from: "Toothpick"

2A^2 + A - 1
(A+1)(2A-1) = 0

that makes 2A^2 - 1 =0

Edit: OH MY BAD AGAIN.

Making too many mistakes the day before the exam  :x
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BenBenMan

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how the eff do i teach myself trig in an hour
« Reply #23 on: November 08, 2007, 05:53:26 pm »
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It took me a few tries but I got there in the end:
[img]http://img406.imageshack.us/img406/4408/bastardequationpa2.th.png[/img]

Gah, beaten to it again :P
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Fitness

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how the eff do i teach myself trig in an hour
« Reply #24 on: November 08, 2007, 05:54:46 pm »
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Quote from: "BenBenMan"
It took me a few tries but I got there in the end

Not to mention helping me at the same time :P Thx Ben
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Toothpaste

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how the eff do i teach myself trig in an hour
« Reply #25 on: November 08, 2007, 05:56:16 pm »
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Quote from: "BenBenMan"
Gah, beaten to it again :P


Sorry! Lol.
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costargh

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how the eff do i teach myself trig in an hour
« Reply #26 on: November 08, 2007, 05:59:52 pm »
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=P vista
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Fitness

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how the eff do i teach myself trig in an hour
« Reply #27 on: November 08, 2007, 06:22:14 pm »
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Quote from: "costargh"
=P vista

=P no it isn't. Office 2007. Close though.
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BenBenMan

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how the eff do i teach myself trig in an hour
« Reply #28 on: November 08, 2007, 07:16:40 pm »
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Quote from: "Fitness"
Quote from: "costargh"
=P vista

=P no it isn't. Office 2007. Close though.


Ya, I wouldn't touch Vista with a 10 foot pole ... but Office 2007 on the other hand is the best thing ever. :D
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kingmar

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how the eff do i teach myself trig in an hour
« Reply #29 on: November 08, 2007, 07:55:12 pm »
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Quote from: "Toothpick"
(cosx)^2 + (sinx)^2 = 1
=> (cosx)^2 = 1 - (sinx)^2

...blah blah blah tons of working out...

sinx = -1 over the given domain
x = 3pi/2

sinx = 0.5
x = pi/6
and x = 5pi/6


Well done. Perfect explanation.

Didn't think you could factorise trigs, but when anything equals "u" anything goes...

Otherwise, I think it unlikely identities are going to be on the exam. Still, cramming them because we don't get much practice on em.

Someone is 50 bound. Toothpick, you're on.
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