Question

Diketahui cos 2 alpha = -7/9, alpha sudut lancip.
Ditanya cos alpha, sin alpha, tan alpha

Answer 1

Cos2a = -7/9
2cos^2 a - 1 = -7/9
2cos^2 a = 2/9
cos^2 a = 1/9
cos a = 1/3 (kuadran 1)

sin^2 a + cos^2 a = 1
sin^2 a = 1 - cos^2 a
sin^2 a = 1 - (1/3)^2
sin^2 a = 8/9
sin a = (2V2)/3

tan a = sina/cosa = [(2V2)/3]/(1/3)
= [(2V2)/3 . 3]
= (2V2)

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