# trig identities questionWatch

Thread starter 4 years ago
#1
removed
0
4 years ago
#2
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
0
4 years ago
#3
for cos, use the identity

EDITED
0
4 years ago
#4
(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...
0
4 years ago
#5
(Original post by AlphaMolecule)
i've got to sin2Î¸ = -0.5, 1
the range is -180<Î¸<180 so do I plot for -360<2Î¸<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
0
4 years ago
#6
the latter
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