Solved, thank you Watch

The Muffin Man_
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#1
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Edit: solved
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EEngWillow
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#2
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Part 1 shows you that the equation you have to solve in the second part, can be written as 4cos^2x-9cosx+2 = 0.

If you let cos(x) = t, and rewrite the equation, the solution should become clearer.
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goodboy4444
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hint: Its a quadratic equation!
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gozatron
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(Original post by The Muffin Man_)
Hi there, I have this question (shown below) for which 8(a) I've solved and got the required solution, but am not sure how this is used in 8(b) and what to do in 8(b) - could someone help me with this, please?

Think about what Sin^2(x) is equal to.
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Hemzo
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I got: 75.5, 284.5, 435.5 and 644.5 as the answers, is this correct?
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The Muffin Man_
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(Original post by EEngWillow)
Part 1 shows you that the equation you have to solve in the second part, can be written as 4cos^2x-9cosx+2 = 0.

If you let cos(x) = t, and rewrite the equation, the solution should become clearer.
I have cos(x) = 1/4 (disregarding cos(x) = 2) and have got 75.5 from the inverse. Now I'm just not sure of how you take 75.5 from 360/add to 360 and whatnot for the solutions...
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littlebeckelina
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You now have the same terms in one equation so like a normal quadratic equation just factorise, don't get put off by the fact it's cosx and cos^2x you can do it
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goodboy4444
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(Original post by Hemzo)
I got: 75.5, 284.5, 435.5 and 644.5 as the answers, is this correct?
:yes:
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EEngWillow
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(Original post by The Muffin Man_)
I have cos(x) = 1/4 (disregarding cos(x) = 2) and have got 75.5 from the inverse. Now I'm just not sure of how you take 75.5 from 360/add to 360 and whatnot for the solutions...
Draw the graph. Always helps if you aren't sure.
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Nomolos
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Remember that sin^2 x = 1 - cos^2 x.
So, substitute it in!
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The Muffin Man_
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(Original post by EEngWillow)
Draw the graph. Always helps if you aren't sure.
Ah that helped immensely; I have all of the solutions now. Thank you very much!
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EEngWillow
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(Original post by The Muffin Man_)
Ah that helped immensely; I have all of the solutions now. Thank you very much!
No problem. Get in the habit of drawing graphs, they help.
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gozatron
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Allow Graphs, CAST diagram is the way forward!
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