Measuring Implications of Triangles

We have stated (in Chapter 6) a minimum measuring rule to apply to price
movements developing from a Head-and-Shoulders Formation, and we can lay down a somewhat similar rule for Triangles — one that applies to both
the Symmetrical and the Right Angle species. The method of deriving the
Triangle formula is not easy to explain in words, but the reader can familiarize himself with it quickly by studying its application on several of the actual
examples which illustrate this chapter. Assuming that we are dealing with
an up-movement (upside breakout), draw from the Top of the first rally that initiated the pattern (in other words, from its upper left-hand corner) a line
parallel to the Bottom boundary. This line will slope up away from the
pattern to the right. Prices may be expected to climb until they reach this
line. Also, as a rule, they will climb, following their breakout from the
pattern, at about the same angle or rate as characterized their trend prior to
their entering the pattern. This principle permits us to arrive at an approximate
time and level for them to attain the measuring line. The same rules
apply (but measuring down, of course, from the lower left corner) to a
descending move.
Although application of the above formula does afford a fair estimate
of the extent of move to be expected from a Triangle, it is neither as definite nor as reliable as the Head-and-Shoulders formula. Do not forget the important
qualification that the Triangle has somehow lost a part of its potential
strength if the breakout is delayed until prices are crowded into the apex.