Definition:Triangle (Geometry)/Right-Angled/Adjacent
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Definition
In a right-angled triangle, for a given non-right angled vertex, the adjacent side which is not the hypotenuse is referred to as the adjacent.
In the above figure:
Also known as
Some older sources, particularly in the context of schoolbooks, refer to the adjacent as the base.
This arises from the habit of orienting the triangle (as is common in such sources) so that its opposite is a vertical line, at the side of the figure (as above).
However, confusion can arise when the triangle is positioned differently, and the angle in question is not at the bottom.
Sources
- 1989: Ephraim J. Borowski and Jonathan M. Borwein: Dictionary of Mathematics ... (previous) ... (next): adjacent: 2.
- 2008: Ian Stewart: Taming the Infinite ... (previous) ... (next): Chapter $5$: Eternal Triangles: The origins of trigonometry
- 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): adjacent side