Asked by ntsoaki
Solve for x if 3sin2x - 3sinx = 2 - 4cosx 0<x<180
Answers
Answered by
Reiny
6sinxcosx - 3sinx = 2 - 4cosx
3sinx(2cosx - 1) = 2(1 - 2cosx)
3sinx(2cosx - 1) - 2(1 - 2cosx) = 0
3sinx(2cosx - 1) + 2(2cosx - 1)
(2cosx - 1)(3sinx + 2) = 0
cosx = 1/2
x = 60° or 300°
or
3sinx = -2
sinx = -2/3, so x is in III or IV
from my calculator, sin 41.81° = +2/3
x = 180+41.81 = 221.81°
or
x = 360-41.81 = 318.19°
3sinx(2cosx - 1) = 2(1 - 2cosx)
3sinx(2cosx - 1) - 2(1 - 2cosx) = 0
3sinx(2cosx - 1) + 2(2cosx - 1)
(2cosx - 1)(3sinx + 2) = 0
cosx = 1/2
x = 60° or 300°
or
3sinx = -2
sinx = -2/3, so x is in III or IV
from my calculator, sin 41.81° = +2/3
x = 180+41.81 = 221.81°
or
x = 360-41.81 = 318.19°
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