"Sub tended" is spelled with the letter combination "b-t" instead of "p-t" because it follows the rule of consonant substitution in English phonetics. The IPA transcription for "sub tended" is /sʌb ˈtɛndɪd/. In this transcription, the "b" sound represents the voiced bilabial stop, while the "t" sound is an unvoiced alveolar stop. This substitution of "b" for "p" is common in English words when the "t" sound appears after "s," as in the case of "sub tender."
"Subtended" is a term typically used in mathematics and geometry to describe the relationship between two points and a geometric figure such as a line, angle, or arc. When two points lie on the same line or curve and the figure is formed by connecting or intersecting those points, we say that the figure is "subtended" by these points.
In more precise terms, "subtended" refers to the action of enclosing or spanning an object, shape, or figure. It describes the process of forming an arc, angle, or line by joining two given points. For instance, if a line is drawn between two endpoints on a circle, it is said to subtend an arc. Alternatively, if a straight line intersects two other lines or rays at different points, it is said to subtend an angle, with the vertex being the common point of intersection.
The word "subtended" derives from the Latin word "subtendere," where "sub" means below or under, and "tendere" means to stretch or extend. Together, these roots reflect the idea of something being extended or stretched beneath or under, indicating the concept of forming a figure by connecting two points.