Question 206389: cos^2x - sin^2x = sin x
with x greater than negative pi and less than or = pi
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! cos^2x - sin^2x = sin x
with x greater than negative pi and less than or = pi
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(1-sin^2(x))-sin^2(x) = sin(x)
1 - 2sin^2(x) = sin(x)
2sin^2(x)+sinx -1 = 0
Factor to get:
(2sin(x)-1)(sin(x)+1) = 0
sin(x) = 1/2 or sin(x) = -1
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If sin(x) = 1/2, x = pi/6 or x = (5/6)pi
If sin(x) = -1, x = (3/2)pi
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Cheers,
Stan H.
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