The true value of h must lie between h′ and hb. Choose a new value of h, and recalculate Q1, Q2, Q3. Then if
Q1 > Q2 + Q3 in case I.,
or
Q1 + Q2 > Q3 in case III.,
the value chosen for h is too small, and a new value must be chosen.
If
Q1 < Q2 + Q3 in case I.,
or
Q1 + Q2 < Q3 in case III.,
the value of h is too great.