page_title: Vertical and horizontal
section_title: In the classroom
hierarchical_section_title: Vertical and horizontal / Mathematical definition / In the classroom
caption_attribution_description: English: a 3d drawing to illustrate the mystery of the horizontal y-axis
context_page_description: In astronomy, geography, and related sciences and contexts, a direction or plane passing by a given point is said to be vertical if it contains the local gravity direction at that point.
  Conversely, a direction or plane is said to be horizontal if it is perpendicular to the vertical direction.
  In general, something that is vertical can be drawn from up to down, such as the y-axis in the Cartesian coordinate system.
context_section_description: In the 2-dimension case, as mentioned already, the usual designation of the vertical coincides with the y-axis in co-ordinate geometry. This convention can cause confusion in the classroom. For the teacher, writing perhaps on a white board, the y-axis really is  vertical in the sense of the plumbline verticality but for the student the axis may well lie on a horizontal table.
caption: The y-axis on the wall is vertical but the one on the table is horizontal
exif: {}