Let I=∫sin(x−3π)cosx1dxI=2∫sin(x−3π)cosxcos3πdx=2∫sin(x−3π)cosxcos(x−3π−x)dx=2∫[sin(x−3π)cosxcos(x−3π)cosx+sin(x−3π)cosxsin(x−3π)sinx]dx=2∫[cot(x−3π)+tanx]dx=2[logsin(x−3π)−log∣cosx∣]+C=2[logcosxsinxcos3π−cosxcosxsin3π]+C=2[log2tanx−3]+C