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数学
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若圆锥的表面积是15π,侧面展开图的圆心角是60°,则圆锥的体积是 ___ .
人气:288 ℃ 时间:2019-10-19 22:01:36
解答
设圆锥的底面半径为r,母线为l,则
2πr=
1
3
πl
,得l=6r,
S=πr
2
+πr•6r=7πr
2
=15π,得
r=
15
7
,圆锥的高h=
l
2
-
r
2
=
35
r
即
h=
35
•
15
7
,
V=
1
3
π
r
2
h=
1
3
π×
15
7
×
35
×
15
7
=
25
3
7
π
.
故答案为:
25
3
7
π
.
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