Positive vector (versin = 1? cos)

Covector (covers = 1？ Sin)

Trigonometric function (trigonometric function)

Also known as loop function. Is the floorboard of sine, cosine, tangent, cotangent, secant, cotangent and other functions. In the plane rectangular coordinate system Oxy, take a point P on the trajectory that forms a positive angle α with the X axis, and the coordinates of P are (x, y) and OP = R, then the sine function SIN α = Y/R, cosine function vers α = r-x/R, tangent function Tan α = Y/X, cotangent function COT α = X/Y, secα = R,.

These eight functions have been completed in the big exam written by 163 1 Xu Guangqi and others. Sine was originally considered as the chord length corresponding to the central angle of a circle. Hippocrates, an ancient Greek astronomer, made this kind of watch in the 2nd century BC, and Ptolemy made watches with intervals of 0 ~ 90 degrees in the 2nd century AD. In the 5th century, the concept of sine was first put forward in India, and a sine function table was given, which was recorded in Suri Calendar (about 400 years). There is also a positive vector function in the book, which is rarely used now. About 5 10 years ago, Indian mathematician Anabodo considered the concept of cosine, which spread to Europe and had many names. It was not unified until 17 century later. Tangent and cotangent functions are caused by the measurement of the sun's shadow. Habbah, an Arabic calculator in the 9th century, compiled the tangent cotangent table for the first time. /kloc-in the 20th century, Abu Wafa independently compiled the first tangent table. Habbah first put forward the concepts of secant and cotangent, which were formally used by Abu Wafa. By 155 1 year, the Austrian mathematician and astronomer Rhaticus had incorporated sine, cosine, tangent, cotangent, secant and cotangent functions into the trigonometric criterion, and attached a secant table. He also defined trigonometric function for the first time with the ratio of side length of right triangle. 1748, Euler first defined trigonometric function by the ratio of function line to radius, making the radius of a circle 1, and created many trigonometric function symbols. At this point, the modern form of trigonometric function began to prevail and developed continuously to this day.