1.

What is the value of 2cos2 15° - 1 ?1. \(\frac 12\)2. \(\frac 1 {\sqrt 2}\)3. \(\frac {\sqrt 3}2\)4. \(\sqrt 3 - 1\)

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

Concept:

2cos2 θ  - 1 = cos 2θ 

 

Calculations:

Consider, 2cos2 15° - 1

= cos 2 (15°) 

= cos (30°) 

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



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