Trigonometric Equations...2

Discussion in 'Geometry and Trigonometry' started by nycmathguy, Dec 28, 2021.

  1. nycmathguy

    nycmathguy

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    Section 5.4

    Screenshot_20211226-094501_Samsung Notes.jpg

    Question 70

    Use: cos(x+A)=cosx.cosA–sinx.sinA

    Let A = pi

    cos(x + pi) = cosx(-1) - sinx(0)

    cos(x + pi) = -cosx

    -cosx - cosx - 1 = 0

    -2cos x - 1 = 0

    -2 cos x = 1

    cos x = -1/2

    Solutions from 0 to 2pi but not including 2pi:

    x = 2pi/3, 4pi/3

    You say?
     
    nycmathguy, Dec 28, 2021
    #1
  2. nycmathguy

    MathLover1

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    correct
     
    MathLover1, Dec 28, 2021
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    nycmathguy likes this.
  3. nycmathguy

    nycmathguy

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    Wonderful. Before moving on to Section 5.5, there are several interesting questions at the end of Section 5.4 for which Ron Larson did not provide sample problems for me to use as a guide.
     
    nycmathguy, Dec 28, 2021
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