Question

14. Using the formula, cos A = /
1 + cos 2 A
-, find the value of cos 30º, it
being given that cos 60°=
​

Answer 1

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Given Formula : cosA = √1 + cos2A / 2

Also, cos60 = 1/2

Required to find : cos30 ]

Now,

Let A = 30 , 2A = 60°

cosA = √1 + cos2A / 2

cos30 = √( 1 + 1/2 ) / 2

cos30 = √(3/2)/2

cos30 = √(3/4) = √3 / 2

Therefore , cos30 = √3/2

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Answer 2

Answer:

Step-by-step explanation: