cos x : sin^2 x=1:2
a) rewirte the equation in form a cos^2 x+b cos x+c
b) find the value of x
cos x : sin^2 x=1:2 for 180<360
Maths,,,,,20marks come and get it,,,,急呀.,,,,PLZ,,,HELP
2007-11-11 8:47 pm
回答 (1)
2007-11-11 8:57 pm
✔ 最佳答案
cos x : sin^2 x=1:2cos x : (1- (cosx)^2) = 1:2
2cos x = 1- (cos x)^2
(cos x)^2 + 2 cos x - 1 = 0
cos x = [-2+sqrt(4+4)]/2 or [-2-sqrt(4+4)]/2
cos x = -1 + sqrt(2) or -1-sqrt(2) (rejected)
x = 294.47 degrees
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