Talk:Hatch mark

Current quote: Hatch marks, sometimes also called tally marks, hash marks, or tick marks, are short line segments, or tiny crossed line segments, used in geometry to indicate relationship or location in a diagram or to show unit divisions on lines, congruency of parts, and points of change in mathematical diagrams.

Comment: Tally marks are not also called hatch marks. However, hatch marks can be thought of as using tally marks. The two are not interchangable. One contains the other. The current quote is like saying cube roots are also called radical signs. Radical signs are a symbol used in cube roots, but cube roots are not radical signs.

Hatch marks are used three distinct ways: as unit markers, congruency markers, and markers of points (usually points of change). All three usages are in geometry. Unit markers are in number theory as well. Points are in graph theory which falls in statistics/data analysis, cartesian algebra, and other stuff. The current usage sentence in the aricle is very confusing and crosses itself.

Current quote: Larger hatch marks may be used to clarify the position of whole numbers while smaller hatch marks may be used to show the position of fractional numbers. Many different patterns are possible and are used. Hatch marks may or may not be labeled. If not labeled, the pattern of the marks tells the viewer the value of the number line at the location marked by a specific hatch. For example:

Comment: This is true for only the usage of hatch marks as unit markers. The example shows a number line, but it does not show a hatch pattern. The example needs to be moved to a more appropriate place. But it is a good example.

Current Quote: Considering the close relationship of geometry to art, hatch marks can probably be traced to hatching in which the pattern of the marks is representative of a unique tone or hue with different patterns indicating different tones. Likewise in geometry, each hatch pattern is representative of a unique value. When hatch marks match, values for the two items or locations are the same. For example, if two triangles are drawn, the first pair of congruent sides can be marked with a single hatch mark on each. The second pair of congruent sides can be marked with two hatch marks each. The patterns are not alike: one pair uses one mark while the other pair uses two marks (Figure 1). This use of pattern makes it clear which sides are the same length even if the sides cannot be measured.

Comment: Thanks for the graphic. Great job. I may add some text. Feel free to add a matching graphic. I'm great at making them, just don't know how to add them.

Current Quote: Hatch marks in geometry follow the usage of Roman numerals with some exceptions. These marks are without serifs and some are not used -- for example, the numbers I, II, III, V, and X are used, but IV and VI are not used since a rotation of 180 degrees can make a 4 easily confused with a 6.

Comment: Thanks for the linking work.

Current Quote: Line graphs may sometimes use hatch marks (Figure 2) as points of change (the points where the line segments of the graph meet end-to-end).

Comment: This has been over-simplified and not adequately explained. The picture also gives the wrong impression. It is not wrong, but it is not the simple idea originally expressed. The picture is a much more complex idea. I'll update the text. Please update the picture since I don't know how.

User:68.93.167.67|68.93.167.67]] 15:14, 13 September 2006 (UTC) Tonea

Suggested merge

I suggest we merge Hash mark into Hatch mark, because they overlap and the latter is more comprehensive. -- Avenue 12:31, 20 February 2007 (UTC)

Comment: I took the liberty of adding a paragraph into the 'congruence notation' section to warn against an 'assuming the inverse' fallacy which can be a tempting conclusion otherwise. -geometry teacher

— Preceding unsigned comment added by 64.6.114.149 (talk) 13:29, 23 October 2015 (UTC)