VECTOR CALCULUS
10.23 The tangent vectors are as follows: foru= 0, the line joining (1, 0 ,0) and
(− 1 , 0 ,0); forv= 0, the line joining (1, 0 ,0) and (∞, 0 ,0); forv=π/2, the line
(0, 0 ,z); forv=π, the line joining (− 1 , 0 ,0) and (−∞, 0 ,0).
ψ(u)=2tan−^1 eu+c,derivedfrom∂[coshu(∂ψ/∂u)]/∂u=0.