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how the eff do i teach myself trig in an hour

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melanie.dee:
gar does someone want to post their working out, i couldnt do it :(

Toothpaste:
(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

Fitness:

--- Quote from: "Toothpick" ---
2A^2 + A - 1
(A+1)(2A-1) = 0
--- End quote ---

that makes 2A^2 - 1 =0

Edit: OH MY BAD AGAIN.

Making too many mistakes the day before the exam  :x

BenBenMan:
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

Fitness:

--- Quote from: "BenBenMan" ---It took me a few tries but I got there in the end
--- End quote ---

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

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