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    Trigonomerty HL em1234

    cos2A = cos(squared)A - sin(squared)A

    Im no confused on this could someone explain/ help

    1. avatar image

      JackW

      Cos(2A) is the same as cos(A+A)

      Cos(A+B)=CosA.CosB-SinA.SinB

      Replace B with A

      Cos(A+A)=CosA.CosA-SinA.SinA

      Cos(2A)=Cos(squared)A-Sin(squared)A

    2. avatar image

      JackW

      We use the identity that says Cos(A+B)=CosA.CosB-SinA.SinB to rewrite the identity and then simplify the expression

    3. avatar image

      em1234

      thank you !!

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      Me

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