question number 19 Rs Aggarwal exercise 11
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Hey there ur answer is here..
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
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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