∫（1-x^2）^0.5dx
设 x=sint t∈[-π/2,-π/2]则
dx=costdt
=∫[cost * cost dt
=∫[(cos2t+1)/2]dt
=∫(1/2)cos2t+(1/2) dt
=(1/4)sin2t+(1/2)t+C
t=arcsinx
=(1/2)x√(1-x²)+(1/2)arcsinx+C