>>792
  (dx/dt)^2=4t^2cos^2t+4t(1-t^2)sintcost+(1-t^2)^2・sin^2t
+」(dy/dt)^2=4t^2sin^2t-4t(1-t^2)sintcost+(1-t^2)^2・cos^2t
4t^2+(1-t^2)^2
よって
L=∫[0.1]√{4t^2+(1-t^2)^2}dt
=∫[0.1]√(t^2+1)dt
=[1/3t^3+t][0.1]
=4/3