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21 June, 01:49

Solve:

sin5x - cos2x + sin x = 0.

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Answers (1)
  1. 21 June, 04:36
    0
    x = 10, 45 degrees.

    Step-by-step explanation:

    This seems a tricky one.

    I guess we can use sin A + sin B = 2 sin (A+B) / 2 cos (A - B) / 2

    so sin 5x + sin x = 2 sin 3x cos 2x so our equation becomes

    2 sin 3x cos 2x - cos 2x = 0

    cos 2x (2 sin 3x - 1) = 0

    so 2 sin 3x = 1

    sin 3x = 1/2

    giving 3x = 30 degrees and x = 10 degrees

    or cos 2x = 0

    so 2x = 90

    giving x = 45 degrees.
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