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SAT math question: "Solve for x" SAT math question: "Solve for x"
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Old 07-14-2008, 06:27 PM   #1
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SAT math question: "Solve for x"
2sin(x) - sin(2x) = 4/pi

or rewritten as

2sin(x) - 2sin(x)cos(x) = 4/pi

or rewritten as

2sin(x)[1 - cos(x)] = 4/pi


thanks!
Last edited by alipes07; 07-14-2008 at 06:28 PM. Reason: more
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Old 07-14-2008, 06:42 PM   #2
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I'm at a loss. The answer is x = 1.238 or 2.808 +/- 2pi. I don't know of any irrational numbers like that from memory.
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Old 07-14-2008, 06:53 PM   #3
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How did you solve it?
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Old 07-14-2008, 06:55 PM   #4
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I graphed 2sin(x) - sin(2x) and 4/pi separately and used the intersection finder on my calculator.
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Old 07-14-2008, 06:57 PM   #5
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Thats a SAT math??
do you mean ACT? because i have never seen any trig on the SAT
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Old 07-14-2008, 07:01 PM   #6
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Its DEFINITELY on both the SAT and ACT


thanks arnoc, but I was thinking of doing it w/out the calculator(even though you can use it, obviously)
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Old 07-14-2008, 07:04 PM   #7
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My strategy was to figure out the number and then work backwards or try to figure out what the "exact" answer would be in terms of a radical or something. The only problem is that I have no idea what solution would come close to yielding those numbers, so I'm doubting that it could be solved without a calculator.
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Old 07-14-2008, 07:07 PM   #8
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I used the solve( operator on my amazing TI-89 Titanium and yielded the same results as arnoc (though there are more answers due to the nature of pi).
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Old 07-14-2008, 08:23 PM   #9
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a personal strategy i find VERY helpful, developed naturally is that whenever i find questions that require to solve for X, and it has only the same variable(meaning, can be XX-5X), i move everything to the left, use the solver function of TI 83, find the X to make the equation zero.
idk if theres 2 answers,but in less than 10 seconds,i got x=2.80812....

No,this kind of question will NOT show up on the SAT.
alipes, its not gona be there. maybe in SAT 2...not SAT 1
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Old 07-14-2008, 08:26 PM   #10
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I hate the solver. I graph everything.
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Old 07-14-2008, 08:39 PM   #11
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Ren, in answer to your idk, there's actually an infinite amount of answers. You know... 2pi, the unit circle? Good times.

Still a not-fun question =/.
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Old 07-14-2008, 09:28 PM   #12
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This isn't SAT math...lol
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Old 07-14-2008, 11:20 PM   #13
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thank you...thats what i was sayin!!
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Old 07-14-2008, 11:22 PM   #14
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I thought you weren't supposed to post homework help questions here? (Or I would have a long time ago)
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Old 07-14-2008, 11:27 PM   #15
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^ ouch...he just tricked us all making us think it was an SAT question..

..while it was his homework?
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