SOLUTION: Verify the following identity by using an angle sum identity: cos (2x) = 1

SOLUTION: Verify the following identity by using an angle sum identity: cos (2x) = 1 - 2(sin2 x). Hint (2x = x + x)

Question 1141650: Verify the following identity by using an angle sum identity: cos (2x) = 1 - 2(sin2 x). Hint (2x = x + x)
Answer by ikleyn(52798) (Show Source): You can put this solution on YOUR website!
.

First step is to write the basic formula correctly:


    cos(2x) = 1 - 2*sin^2(x).


    //  In your post the formula is presented by incorrect way !



Second step is verification


    cos(2x) = cos(x+x) = cos(x)*cos(x) - sin(x)*sin(x) = cos^2(x) - sin^2(x) = (1-sin^2(x)) - sin^2(x) = 1 - 2*sin^2(x).


QED.

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