Chord value is the value that the length of the opposite side in a right triangle is greater than the length of the hypotenuse. The sine value of any acute angle is equal to the cosine value of other angles, and the cosine value of any acute angle is equal to the sine value of other angles, which is usually represented by the symbol sin. Sinθ can also be understood as the ratio of the area of a unit isosceles triangle with the vertex angle θ to the area of a unit isosceles right triangle. The special angle of sine value has a direct result. For example: SIN 30 = 1/2, SIN 45 = √ 2/2, SIN 60 = √ 3/2, SIN 90 = 1, SIN 180 = 0, SIN 0 = 0, SIN 270 = but some of them are not special angles, so Because 40 degrees is not a special angle, the approximate algorithm is 40 degrees = 45 degrees -45 degrees * (45-40) π/180 = √ 2/2-5 √ 2π/360.
Trigonometric function is one of the basic elementary functions, with angle as the independent variable, and the coordinates corresponding to the intersection of the terminal edge of any angle and the unit circle or its ratio as the dependent variable. Common trigonometric functions are sine function, cosine function and tangent function. Trigonometric functions are generally used to calculate the sides and angles of triangles with unknown lengths, and are widely used in navigation, engineering and physics.