Question 1063062: What is the exact value of sin(-7pi/12) and how do you find it? Found 3 solutions by rothauserc, ikleyn, math_helper:Answer by rothauserc(4718) (Show Source):
You can put this solution on YOUR website! pi is 180 degrees
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180 / 12 = 15 and -7 * 15 = -105
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360 + (-105) = 255
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255 is in the third quadrant where the sin is negative
:
sin(255) = −0.9659
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Exact value of sin(-7pi/12) is
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To find , use the formula of half argument for cosines
(see the lesson Trigonometric functions of half argument in this site):
cos^2(15°) = (1+cos(30°)/2 = = .
Hence,
cos(15°) = .
Thus = .
You can put this solution on YOUR website! (because sin(-a) = -sin(a))
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Use sin(a+b) = sin(a)cos(b) + cos(a)sin(b) :
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Use these 3 facts:
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Continuing…
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