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3 sinØ = 1.5 , 0 ≤ Ø ≤ 4
sinØ = 1.5/3 = .5
the sine is positive in I or II
Ø = π/6 or Ø = π - π/6 which is 5π/6
the period of sinØ is 2π, so adding another 2π to π/6 yields 13π/6 , which would be beyond your upper domain value of 4
Ø = π/6 , 5π/6