23.利用欧拉公式 24.(1)、2 bdudv cosa+rcosv 26.K=1/R=H 27.(1) K=f(gf"-g"f)/g( g(g"f'-f"g')/f'(g"2+f2)]/2g(g (2)K=-b2/(b2+y2)2;H=0, (3)K=-1/(1+2u2)2;H=(u2+1)/(2u2+1) 29N=0.Il=M2,I>0 30. K=c /(a-cos'v+cosin v) 补充题 1.√Edu±√Gdvy=0 将 {ru,r、} Schm 正 交 n/√E; Er)√EG-F 3.u线δv= 4.H2=(1+22)2/4=K=入23. 利用欧拉公式. 24. (1) − + − 2 2 2 bdudv 2 b v ; (2) - cosv(a + rcosv)du rdv ; 2 (3) −4 + + + − 2 2 2 2 2 2 ab / a b b (u v) a (u v) 26. K=1/R=H. 27. (1) K f g f g f g g f H g g f f g f g f g g f =    −    +  =   −     +   +  ( ) / ( ) ; [ ( ) / ( )]/ ( ) ; / 2 2 2 2 2 2 2 3 2 2 (2) K = −b b + v H = 2 2 2 2 / ( ) ; 0; (3) K = −1 1+ 2u H = u +1 2u +1 2 2 2 2 3 2 / ( ) ; ( ) / ( ) / . 29. N=0. II=-M2 , I>0. 30. K=c2 /(a2cos2v+c2 sin2v)2 . 补充题 1. Edu Gdv = 0. 2. 将 {r ,r }Schmidi u v 正交化， e1 r u E Fru E Er v EG F 2 = / ; e 2 = (− / ,+ ) − . 3. u 线v=0. 4. H K 2 1 2 2 = + 4 = = 1 2  1 = 2 (  ) /    