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प्रश्न
Find A, if 0° ≤ A ≤ 90° and 2 cos2 A – 1 = 0
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उत्तर
2 cos2 A – 1 = 0
`=> cos^2A = 1/2`
`=> cosA = 1/sqrt(2)`
We know `cos 45^@ = 1/sqrt(2)`
Hence, A = 45°
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