Simplify cos(2a)

Problem

cos(2*a)

Solution

1. Identify the expression as a double angle trigonometric function for cosine.

2. Apply the double angle formula for cosine, which has three common equivalent forms.

3. Select the primary form based on the Pythagorean identity sin2(a)+cos2(a)=1

4. State the alternative forms by substituting the identity into the primary form.

Final Answer

cos(2*a)=cos2(a)−sin2(a)

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