∫ 2 cos x sin(1 - 2x) dx = ....

Ingat!

Sifat–sifat Trigonometri berikut:

2 cos α sin β = sin(α + β) - sin(α - β)

Maka:

2 cos x sin(1 - 2x) dx = sin(x + 1 - 2x) - sin(x - (1 - 2x)) dx

                                   = sin(-x + 1) - sin(3x - 1) dx

                                   = cos(-x + 1) + cos(3x - 1) + c

                                   = cos(x - 1) + cos(3x - 1) + c