SOLUTION: Find all real numbers in the interval [0, 2pi] which satisfy the following equation. Use special angles. 2cos2x+1=0

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Question 834508: Find all real numbers in the interval [0, 2pi] which satisfy the following equation. Use special angles.
2cos2x+1=0

Answer by lwsshak3(11628)   (Show Source): You can put this solution on YOUR website!
Find all real numbers in the interval [0, 2pi] which satisfy the following equation. Use special angles.
2cos2x+1=0
cos2x=-1/2
2x=2π/3,4π/3 (in quadrants II and III in which cos<0)
x=π/3,2π/3

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