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Mathematics - Trigonometric Ratios & Identities Question with Solution | TestHub

MathematicsTrigonometric Ratios & IdentitiesAddition, Multiplication, Subtraction formula based,Multiple/Submultiple anglesMedium2 minQB

MathematicsMediummultiple choice

If $cos β$ is the geometric mean of $sin α$ and $cos α$ , where $0 < α, β < π /2$ , then $cos 2 β =$

Options:(select one or more)

Answer:

A, B

Solution:

$cos^{2} β = sin α cos α$ , so $cos 2 β = 2 cos^{2} β - 1 = sin 2 α - 1 = - 2 sin^{2} (π /4 - α) = - 2 cos^{2} (π /4 + α)$ .

Stream:JEESubject:MathematicsTopic:Trigonometric Ratios & IdentitiesSubtopic:Addition, Multiplication, Subtraction formula based,Multiple/Submultiple angles

⏱ 2mℹ️ Source: QB

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