trig identities question Watch

AlphaMolecule
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#2
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convert everything to sin or cos (I would probably go for cos in this case)

rearrange to get a quadratic in cos(2x) that's equal to 0

solve for cos(2x) and use those values to find x
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Hasufel
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for cos, use the identity \cos^{2}(2 \theta)=1- \sin^{2}(\theta)

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Hasufel
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(Original post by Arithmeticae)
convert everything to sin or cos (I would probably go for cos in this case)

rearrange to get a quadratic in cos(2x) that's equal to 0

solve for cos(2x) and use those values to find x
this also...
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(Original post by AlphaMolecule)
i've got to sin2θ = -0.5, 1
the range is -180<θ<180 so do I plot for -360<2θ<360 and then divide the answers by 2?

if so I got 45, 105, 135, -15, -75 and -135
yep, exactly

i haven't checked but your method looks fine
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Hasufel
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the latter
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