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How are these solved?

1. cosx+1=0; x ∈ R
2. 4sin^2 x - 1 = 0; x ∈ R
3. 2cos^2 x + 3cosx + 1 =0;0 ≤ x < 2π

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1 answer

  1. cosx+1 = 0
    cosx = -1

    4sin^2x-1 = 0
    sinx = ±1/2

    2cos^2x+3cosx+1 = 0
    (2cosx+1)(cosx+1) = 0
    cosx = -1/2 or -1

    Now find angles in the proper quadrants for those solutions.
    And don't forget your Algebra I now that you're doing trig!

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