Question

34) Prove that 2cos20 -1 = cos2o-sin.​

Answer 1

Answer:

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Step-by-step explanation:

The cosine double angle formula is cos(2theta)=cos2(theta) - sin2(theta). Combining this formula with the Pythagorean Identity, cos2(theta) + sin2(theta)=1, two other forms appear: cos(2theta)=2cos2(theta)-1 and cos(2theta)=1-2sin2(theta).