当，为的k阶无穷小，则。

由曲线[imgwidth="53"height="24"src="https://p.ananas.chaoxing.com/star3/origin/db4fa8875f945a05a5a4e1267be38b73.png"]、[imgwidth="37"height="21"src="https://p.ananas.chaoxing.com/star3/origin/8951f704839e2c8e32609744580906d7.png"]和[imgwidth="37"height="19"src="https://p.ananas.chaoxing.com/star3/origin/e2a3aace4ad8b56317c5010b305a51ae.png"]围成的平面图形绕[imgwidth="15"height="17"src="https://p.ananas.chaoxing.com/star3/origin/b3048d8c2bbe74ff01f7d3c8915bfdef.png"]轴旋转一周所得旋转体的体积[imgwidth="28"height="19"src="https://p.ananas.chaoxing.com/star3/origin/c9d9123939953c49b1e9b6492e79f835.png"](). A: imgwidth="35"height="41"src="https://p.ananas.chaoxing.com/star3/origin/2d760dcf355fa1cf2500875442f19085.png">; B: ; C: ; D: .

由曲线[imgwidth="156"height="53"src="https://p.ananas.chaoxing.com/star3/origin/00e346dd386ef544f5052fb5c90e1372.png"]、[imgwidth="37"height="19"src="https://p.ananas.chaoxing.com/star3/origin/8fad2786802119320b27fc6647707e0d.png"]和[imgwidth="35"height="21"src="https://p.ananas.chaoxing.com/star3/origin/27d8820aa177e50656e6ffa3c6225a67.png"]围成的平面图形绕[imgwidth="15"height="17"src="https://p.ananas.chaoxing.com/star3/origin/b3048d8c2bbe74ff01f7d3c8915bfdef.png"]轴旋转一周所得旋转体的体积[imgwidth="28"height="19"src="https://p.ananas.chaoxing.com/star3/origin/c9d9123939953c49b1e9b6492e79f835.png"](). A: imgwidth="55"height="21"src="https://p.ananas.chaoxing.com/star3/origin/3bcbb56de7b78a2ff7eff984ee56642e.png">; B: ; C: ; D: .

若时，与为等价无穷小，则[imgwidth="56"height="16"src...e01574f30fc078.png"]

设则（　　　[imgwidth="102"height="54"src="htt...9d4a97a5a3524b.png"]