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2cos^2A-cos2A-1=0 Help
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2cos^2A-cos2A-1=0
Help

User Xyphoid
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1 Answer

10 votes

Answer:

steps below

Explanation:

Are you going to solve the value of A or just a proof the equation

cos 2A = cos² A - sin² A

2cos²A-cos2A-1 = 2cos²A - (cos² A - sin² A) - 1 = cos² A + sin² A - 1

2cos²A-cos2A-1 = 1 - 1 = 0

A: 90° or 270° or 450° .....

User Manish Karena
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