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Math

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Which of the following is a solution to the trigonometric equation
2cos2 x - 5cos x + 2 = 0?

A) 240 degrees
B) 135 degrees
C) 270 degrees
D) 90 degrees

  • Math - ,

    I will read that as
    2cos^2 x - 5cos x + 2 = 0
    (2cosx - 1)(cosx - 2) = 0
    cosx = 1/2 or cosx = 2, the last part of course is not possible

    so cosx = 1/2
    x = 60° or 300°

    So none of your choices work.
    Both of my answers work in the original equation.
    Check your typing

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