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Babynini
 one year ago
5cos2(theta)=2
Find all solutions in interval [0,2pi)
Babynini
 one year ago
5cos2(theta)=2 Find all solutions in interval [0,2pi)

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Babynini
 one year ago
Best ResponseYou've already chosen the best response.1so cos2(theta)=2/5 2(theta)= ?

Babynini
 one year ago
Best ResponseYou've already chosen the best response.1@peachpi it's a little different.. :P

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Is that cos 2Θ or cos² Θ?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0ok. so the first thing I like to do when Θ is multiplied is "fix" the interval. 0 ≤ x < 2π Since the x is multiplied by 2, multiply the whole interval by 2 to get 0 ≤ 2x < 4π

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0so we do the same thing we did last time, except now we're looking for solutions from 0 to 4pi. cos 2Θ = 2/5 2Θ = arccos (2/5)

Babynini
 one year ago
Best ResponseYou've already chosen the best response.1arccos(2/5) = 1.159 so we want to add pi to this?

Babynini
 one year ago
Best ResponseYou've already chosen the best response.1or, sorry, subtract this from 2pi

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0You want to divide that by 2 Θ = ½ arccos (2/5) → answer in 1st quadrant on the interval from 0 to 2pi Then add 2pi to get the 1st quad angle between 2pi and 4pi

Babynini
 one year ago
Best ResponseYou've already chosen the best response.1em so the original answer is 0.579 adding 2pi = 6.862

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0the 0.579 is right. and you actually subtract it from 2pi to get the other answer

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Yes. 5.8 :) There are going to be two more solutions. You got 2Θ = 1.159. Add 2pi to that, then divide by 2 to get the corresponding Θ.

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0and then (2pi  1.159)/2 for the 4th solution is 2.56

Babynini
 one year ago
Best ResponseYou've already chosen the best response.1K so it's theta = 1.159/2 = 0.579 So our first answer: 5.8 add 2pi to that: 3.72 next we have 2pi0.58 = 5.70 (our third answer) then 5.70  pi = 2.56 (our fourth answer) haha sorry that's all jumbled up.

Babynini
 one year ago
Best ResponseYou've already chosen the best response.1= 0.58, 3.72,5.70,2.56

Babynini
 one year ago
Best ResponseYou've already chosen the best response.1I'll get this. Sometime. thanks!

Babynini
 one year ago
Best ResponseYou've already chosen the best response.1@peachpi I just did one by myself!! and got the right answer! xD :')
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