Trigonometry in JavaScript

Trigonometry mainly studies triangles and their corner relationships, which contain a 90-degree angle triangle called right triangle. Here the main research right triangle related knowledge.

　　　1. Angles and radians

360 (angle) = 2*math.pi (radians)　

degrees = radians * 180/math.pi angle equals radians multiplied by 180 again except for Piradians = degrees * math.pi/180 radians equals angle degree multiplied by PI and removed in 180

　　　2. Edges of triangles

In a right triangle, the two edges adjacent to the 90-degree angle are called right-angled edges, and their corresponding edges are called hypotenuse, and the hypotenuse is always the longest edge.

　　　

　　　3. Trigonometric Functions

sine : The ratio of the edge to the hypotenuse of a corner.

　　　

Sine of a 30-degree angle

Math.sin (* math.pi/180)

　　　

　　　cosine : The ratio of the adjacent edge of a corner to the hypotenuse.

　　　

Cosine of a 30-degree angle

Math.Cos (* math.pi/180)

　　　tangent : The ratio of the pair of edges to the adjacent edges of a corner.

Tangent of a 30-degree angle

Math.tan (* math.pi/180)

　　　sine chord : math.asin (ratio)

　　　inverse cosine : math.acos (ratio)

The inverse of the sine and cosine of the cosine is the inversion of the sinusoidal, and a ratio is entered to obtain a radian of the corresponding angle.

Math.sin (math.pi/180)//approx. 0.5  math.asin (0.5) * 180/math.pi//approx. 30 degrees

　　　anyway cut : Math.atan (ratio)

Tangent angle is rounded by the ratio of the edge to the neighboring edge of a corner.

Math.tan (math.pi/180)//approx. 0.578  Math.atan (0.578) * 180/math.pi//approx. 30 degrees

JavaScript in another anyway tangent:math.atan2 (y,x)　　

The coordinate system in JavaScript is not the same as usual.

　　　　

　　　

Calculates the angle of a point of change in a JavaScript coordinate system by using an inverse tangent (math.atan2) that corresponds to a fixed point:

Fixed point (arrow.x, ARROW.Y)

Change Point (mouse.x, MOUSE.Y)

var dx = mouse.x-arrow.x,    dy = mouse.y-arrow.y,    angle = math.atan2 (dy, dx); Console.log (' angle: ' + angle ');

In JavaScript calculations,math.atan2 (y, x) can correctly calculate the corresponding angle.

　　　4. Pythagorean theorem

　　　In right triangle, the square of two right-angled sides equals the square of the hypotenuse.

　　　

　　　Squared of a squared + b = Square of C

　　　Calculate the distance between two points

Point 1: (x1, y1)

Point 2: (x2, y2)

var dx = x2-x1,    dy = y2-y1,    dist = math.sqrt (dx * dx + dy * dy); Console.log (' Distance: ' + dist);  

Trigonometry in JavaScript