Question

Using the formula cos A is equal to plus or minus square root of oneplus cos2a bye tu find the value of cos67 1/2 degrees

Answer 1

Answer:

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Answer 2

Step-by-step explanation:

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 = \frac {\sqrt 3} { 2 }

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