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i’m confused on this question. i’m taking a pretest and i haven’t fully learned this material, help!! thank you :) !

i’m confused on this question. i’m taking a pretest and i haven’t fully learned this-example-1
User Tim Reynolds
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1 Answer

8 votes
8 votes

we have the expression


cos(x)-cos^3(x)

Remember that


\begin{gathered} sin^2x+cos^2x=1 \\ cos^2x=1-sin^2x \end{gathered}

substitute in the given expression


\begin{gathered} cos(x)-cos^(3)(x) \\ cos(x)-cos^2(x)cos(x) \\ cos(x)-(1-sin^2x)cosx \\ cosx-cosx+cosxsin^2x \\ cosxsin^2x \end{gathered}

therefore

The answer is the first option

User Fore
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