例2计算[4sin√xx 解4sin√xax x=0=02xs入 t=√x,dx=2td =2 tsin tdt 4 =-2 td(cost 2 lt cost+2 2 cos tdt 上一页下一页返回例 2 计算 xdx .  4 0 2 sin  解 t tdt x t x t t x dx tdt  = = = = = = 2 2 0 2 sin 2 , 4 0, 0;, 2    xdx  40 2 sin  2 td(cost) 2 0 = −  t t tdt  = − + 20 20 2 cos 2 cos  