>>489
∫dx/(2+tan(x))=∫cos(x)/{2cos(x)+sin(x)} dx=(1/5)∫2 + {cos(x)-2sin(x)}/{2cos(x)+sin(x)} dx
2cos(x)+sin(x)=t とおくと、dx=dt/{cos(x)-2sin(x)} だから、(1/5)*{2x + log|2cos(x)+sin(x)|}+C