How to pronounce other trigonometric functions: sin [sa? n】、cos [？ Kossa? n].

Sin is short for sine, cos is short for cosine, and tan is short for tangent.

In Rt△ABC (right triangle), ∠C = 90, AB is the opposite side C of ∠ C, BC is the opposite side A of ∠A, AC is the opposite side B of ∠B, and the tangent function is tanB=b/a, that is, tanB=AC/BC.

Tan origin:

From the 5th century to12nd century, Indian mathematicians made great contributions to trigonometry. Although trigonometry was still a computing tool and an accessory of astronomy at that time, the content of trigonometry was greatly enriched through the efforts of Indian mathematicians.

The concepts of sine and cosine in trigonometry were first introduced by Indian mathematicians, who also made sine tables more accurate than Ptolemy.

The chord table made by Ptolemy and Hipparchus is a round full chord table, which corresponds to an arc, and the chord is sandwiched in the middle of the arc. Unlike Indian mathematicians, they correspond the half chord (AC) to the half arc (AD) of the whole chord, that is, AC corresponds to ∠AOC. In this way, they created a sine table instead of a full chord table.