[积分]旋转体积与极限

楼主: skyghostlove (Chris)   2014-12-13 01:13:16
各位好:
以下两题做法可否请帮忙察看是否有错
(1)
Find the volume of the solid generated when the region encolsed by
2
the given curves is revolved about the x axis : y = x , y = 1 ,
x = 0.
我的做法如下
Ans:
1
V=∫ π(y-0)dy
0
1
=∫π(y) dy
0
1
= ──π
2
───────────────────────────────────────
(2)Evaluate the limit
3 x
lim (1- ──)
x→∞ x
我的做法如下
Ans:
3 x
ln(1- ─ )
= lim e x
x→∞
3
xln (1- ─ )
= lim e x
x→∞

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