∫cos^(-1)x dx
=∫secxdx
=ln|secx+tanx|+c
∫cos√x dx
令√x=t,x=t²,dx=2tdt
原式=2∫tcostdt
=2∫tdsint
=2tsint-2∫sintdt
=2tsint+2cost+c
=2√xsin√x+2cos√x+c