Diketahui sin x = 15/17, maka nilai dari cos 2x=... Berapa ya?? Tolong dong jawabannya..

sin x = 15 / 17,
cos 2x = 1 - 2sin^2x
cos 2x = 1 - 2(15/17)^2
cos 2x = 1 - 450/289
cos 2x = - 161/289


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sinx = 15/17
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17² - 15² = 8²
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maka cosx = 8/17

cos2x = cos²x - sin²x
          = (15/17)² - (8/17)²
          = (15/17 + 8/17)(15/17 - 8/17)
          = (23/17) (7/17)
           = 161/289