浅议《切线长定理》教学过程设计
The Designing in Teaching Course of " Qiexian Chang Rule "
Fenchel曾证明，封闭空间曲线的切线象的长不小于2π。
Fenchel proved that the length of the tangent spherical image of a closed space curve is at least 2 π . In this paper , we prove the following theorem .
切线长