The universal formula can turn all trigonometric functions into polynomials with only tan(a/2). Replacing sinα, cosα and tanα with a formula containing tan(α/2) is called universal substitution formula. The general formula makes up the gap between trigonometry and algebra.
Trigonometric function conversion formula: sin (a+b) = sinacosb+cosasinbsin (a-b). Sine, a mathematical term, in a right triangle, the ratio of the opposite side to the hypotenuse of any acute angle ∠A is called sine of ∠A, which is abbreviated from the English word sine, that is, the opposite side/hypotenuse of Sina = ∠ A.
Limit substitution formula: sinx, tanx, 1-cosx 1/2 x 2, e x-1x, ln( 1+x) x, (1+x) n-6544.
Trigonometric function is one of the basic elementary functions, which takes the angle (the most commonly used radian system in mathematics, the same below) as the independent variable, and the angle corresponds to the coordinates where the terminal edge of any angle intersects with the unit circle or its ratio as the dependent variable. It can also be equivalently defined as the lengths of various line segments related to the unit circle.