Solving this equation, we obtain
By adding the last two equations we find
and hence
Using Eqs. (E.42), we derive
Because the direction vector r′ of the line g′ is a unit vector, the length of the shadow
d is equal to v. Therefore we obtain from Eq. (E.48), with some trigonometric operations,
By adding the last two equations we find
and hence
Using Eqs. (E.42), we derive
Because the direction vector r′ of the line g′ is a unit vector, the length of the shadow
d is equal to v. Therefore we obtain from Eq. (E.48), with some trigonometric operations,