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Undry1

5sin2x + 2cosx(2+2cos2x) = 0

5sin2x + 2cosx(2+2cos2x) = 0

5sin2x + 4cosx + 4cos[x]cos[2x] = 0

5sin2x + 4cosx + 4cos[x]cos[2x] = 0

5(2sinxcosx) + 4cosx + 4cos[x](1-2sin²x) = 0

10sin[x]cos[x] + 4cosx + 4cosx - 8cos[x]sin²x = 0

10sin[x]cos[x] + 8cosx - 8cos[x]sin²x = 0

10sin[x] + 8 - 8sin²x = 0

8sin²x - 10sinx - 8 = 0

Let s = sinx

8s² - 10s - 8 = 0

solve this to get s ≈ 1.8042 and -0.554

sinx = -0.554

x = -33.64° etc.

Ricki

5sin2x + 2cosx(2+2cos2x) = 0

5sin2x + 4cosx + 4cos[x]cos[2x] = 0

5sin2x + 4cosx + 4cos[x]cos[2x] = 0

5(2sinxcosx) + 4cosx + 4cos[x](1-2sin²x) = 0

10sin[x]cos[x] + 4cosx + 4cosx - 8cos[x]sin²x = 0

10sin[x]cos[x] + 8cosx - 8cos[x]sin²x = 0

10sin[x] + 8 - 8sin²x = 0

8sin²x - 10sinx - 8 = 0

Let s = sinx

8s² - 10s - 8 = 0

solve this to get s ≈ 1.8042 and -0.554

sinx = -0.554

x = -33.64° etc.

5sin2x + 4cosx + 4cos[x]cos[2x] = 0

5sin2x + 4cosx + 4cos[x]cos[2x] = 0

5(2sinxcosx) + 4cosx + 4cos[x](1-2sin²x) = 0

10sin[x]cos[x] + 4cosx + 4cosx - 8cos[x]sin²x = 0

10sin[x]cos[x] + 8cosx - 8cos[x]sin²x = 0

10sin[x] + 8 - 8sin²x = 0

8sin²x - 10sinx - 8 = 0

Let s = sinx

8s² - 10s - 8 = 0

solve this to get s ≈ 1.8042 and -0.554

sinx = -0.554

x = -33.64° etc.

Out of range.

Dekota

x = 180° + 33.64 = 213.64°

I knew that, just teasing.

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