视距长度:=+L+h2 Rh Rh (有极小值) 12L-l T 0,解此得1 R L +h2) L L=2S T 2(4+、h2)=2S √h+√h2)2=2(12+√1)2=2 最小半径:Rm⚫ 视距长度: (有极小值) 2 1 2 1 2 L l L Rh l Rh S t L t T − = + + = + + 令 = 0, dl dST 1 2 1 h h h l + 解此得 = 2 ( ) 2 ( ) 2 2 1 2 1 2 L h h L h h L R ST + + = + + = 4 2 2( ) 2 2 1 2 min = − + = T − ST h h L S 2( ) 2( 1.2 .1) 2 2 2 h1 + h2 = + = min min L 最小半径: R =