18. Using the formula, cos A=
1 + cos 2A
find the value of cos 30°, it
2
1
being given that cos 60°
2.
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5
Answer: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 =
Step-by-step explanation:
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