What is the value of 2cos

1. \(\frac 12\)

2. \(\frac 1 {\sqrt 2}\)

3. \(\frac {\sqrt 3}2\)

4. \(\sqrt 3 – 1\)

^{2}15° – 1 ?1. \(\frac 12\)

2. \(\frac 1 {\sqrt 2}\)

3. \(\frac {\sqrt 3}2\)

4. \(\sqrt 3 – 1\)

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Correct Answer – Option 3 : \(\frac {\sqrt 3}2\)

Concept:2cos2 θ – 1 = cos 2θ

Calculations:Consider, 2cos2 15° – 1

= cos 2 (15°)

= cos (30°)

= \(\dfrac {\sqrt 3}2\)