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Given x=pi/3, what is the exact value of cos(pi+x)?A. 1/2B. - square root of 3/2C. square root of 3/2D. -1/2

User Magnudae
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1 Answer

4 votes

SOLUTION

The given value is:


x=(\pi)/(3)

It follows that:


\cos(\pi+x)=\cos(\pi+(\pi)/(3))

This gives:


\begin{gathered} \cos(\pi+(\pi)/(3)) \\ =\cos((3\pi+\pi)/(3)) \\ =\cos((4\pi)/(3)) \\ =-(1)/(2) \end{gathered}

Therefore the correct answer is option D

User Roet
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