2sinx = căn3 >>sinx = (căn3)/2 >>sinx = sinpi/3 >>x=pi/3 + k2pi hoặc x = pi - pi/3 + k2pi >>x = pi/3 + k2pi hoặc x = 2pi/3 + k2pi *sinx + căn3.cosx = 2 >>1/2.sinx + (căn3)/2.cosx = 1 >>sinx.cospi/3 + cosx.sinpi/3 = 1 >>sin(x + pi/3) = 1 >>x + pi/3 = pi/2 + k2pi >>x = pi/6 + k2pi
Khó cho chết đi!!

sinx - sin2x + sin3x = 0 >>(sinx + sin3x) - sin2x = 0 >>2sin2x.cosx - sin2x = 0 >>sin2x(2cosx - 1) = 0 >>sin2x = 0 hoặc 2cosx - 1 = 0 *sin2x = 0 >>2x = kpi >>x = kpi/2 *2cosx - 1 = 0 >>cosx = 1/2 >>cosx = cospi/3 >>x = pi/3 + k2pi hoặc x = -pi/3 + k2pi *vậy: x = kpi/2; x = pi/3 + k2pi hoặc x = -pi/3+k2pi

1) sinx - sin2x + sin3x = 0
=> (sinx + sin3x) - sin2x = 0
=> 2sin2x.cosx - sin2x = 0
=> sin2x.(2cosx - 1) = 0
=> sin2x = 0 hoặc 2cosx - 1 = 0
+) sin2x = 0
=> 2x = kπ 
=> x = kπ/2
+) 2cosx - 1 = 0
=> cosx = 1/2
=> cosx = cosπ/3
=> x = π/3 + k2π hoặc x = -π/3 + k2π
Vậy: x = kπ/2
x = π/3 + k2π hoặc x = -π/3 + k2π

sinx - sin2x + sin3x = 0 
=> (sinx + sin3x) - sin2x = 0
=> 2sin2x.cosx - sin2x = 0
=> sin2x.(2cosx - 1) = 0
=> sin2x = 0 hoặc 2cosx - 1 = 0
+) sin2x = 0
=> 2x = kπ 
=> x = kπ/2
+) 2cosx - 1 = 0
=> cosx = 1/2
=> cosx = cosπ/3
=> x = π/3 + k2π hoặc x = -π/3 + k2π

2) sinx + căn3.cosx = 2
=> 1/2.sinx + (căn3)/2.cosx = 1
=> sinx.cosπ/3 + cosx.sinπ/3 = 1
=> sin(x + π/3) = 1
=> x + π/3 = π/2 + k2π 
=> x = π/6 + k2π

3) 2sinx = căn3
=> sinx = (căn3)/2
=> sinx = sinpi/3
=> x = π/3 + k2π hoặc x = π - π/3 + k2π 
=> x = π/3 + k2π hoặc x = 2π/3 + k2π