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# Solution for If θ is a Positive Acute Angle Such that Sec θ = Cosec 60°, Find 2 Cos2 θ – 1 - CBSE Class 10 - Mathematics

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ConceptTrigonometric Ratios of an Acute Angle of a Right-angled Triangle

#### Question

If θ is a positive acute angle such that sec θ = cosec 60°, find 2 cos2 θ – 1

#### Solution

We know that sec (90 – θ) = cosec2 θ

Sec θ = sec (90 – 60°)

On equating we get

Sec θ = sec 30°

𝜃 = 30°

To Find 2 cos2 θ – 1

=> 2 xx cos^2 30^@ - 1    [cos 30 = sqrt3/2]

=>  2 xx (sqrt3/2)^2 - 1

=> 2 xx 3/4  - 1

=> 3/2 - 1

= 1/2

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#### APPEARS IN

Solution If θ is a Positive Acute Angle Such that Sec θ = Cosec 60°, Find 2 Cos2 θ – 1 Concept: Trigonometric Ratios of an Acute Angle of a Right-angled Triangle.
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