12sin的精选

万能代换：令y=tan(x/2)，dx=2dy/(1+y²)，sinx=2y/(1+y²)∫1/(2+sinx)dx=∫[2/(1+y²)]/[2+2y/(1+y²)]dy=∫1/(y²+y+1)dy=(2/√3)arctan[(2tan(x/2)+1)/√3]+C=(2/√3)arctan[(2/√3)tan(x/2)+1/√3]+C解释根据牛顿-莱...