令x=10sint
dx=10cost dt
x=5 -> t=π/6
x=0 -> t=0
5 (1/2) π/6 (1/2)
∫(100-x^2) dx = ∫(100-100sint^2) x (10cost dt)
0 0
π/6 2 2
=∫100(cost) dt 由於cos2t=2(cost)-1
0
π/6
=50∫(cos2t+1) dt
0
π/6
=(25sin2t+50t)|
0
=...........
※ 編輯: twkccy1990 來自: 111.254.221.154 (01/10 02:54)