Giải phương trình lượng giác: Cos2x + sin3x = sin2x - cos3x
________________________
cos2x + sin3x = sin2x - cos3x
<=> cos2x + cos3x = sin2x - sin3x
<=> 2cos5x/2.cos(-x/2) = 2cos5x/2.sin(-x/2)
<=> cos5x/2.cos(-x/2) = cos5x/2.cos(π/2 + x/2)
<=> cos5x/2.[cos(π/2 + x/2) - cos(-x/2)] = 0
<=> cos5x/2 = 0 hoặc cos(π/2 + x/2) = cos(-x/2)
<=> 5x/2 = π/2 + kπ hoặc π/2 + x/2 = -x/2 + k2π hoặc π/2 + x/2 = x/2 + k2π (loại)
<=> x = π/5 + k2π/5 hoặc x = -π/2 + k2π, k nguyên