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Math.atan2 to find direction of a vector

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If you are working with vectors or lines you will at some stage want to get the direction of a vector, or line. Or the direction from a point to another point.

Math.atan(yComponent, xComponent) return the angle in radius within the range of -Math.PI to Math.PI (-180 to 180 deg)

Direction of a vector 

var vec = {x : 4, y : 3};
var dir = Math.atan2(vec.y, vec.x);  // 0.6435011087932844

Direction of a line 

var line = {
    p1 : { x : 100, y : 128},
    p2 : { x : 320, y : 256}
}
// get the direction from p1 to p2
var dir = Math.atan2(line.p2.y - line.p1.y, line.p2.x - line.p1.x); // 0.5269432271894297

Direction from a point to another point 

var point1 = { x: 123, y : 294};
var point2 = { x: 354, y : 284};
// get the direction from point1 to point2
var dir = Math.atan2(point2.y - point1.y, point2.x - point1.x); // -0.04326303140726714
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Arithmetic Math:
* Remarks
* Constants
* Remainder Modulus
* Rounding
* Trigonometry
* Bitwise operators
* Increment
* Exponentiation Math.pow or
* Random Integers and Floats
* Addition
* Simulating events with different probabilities
* Little Big endian for typed arrays when using bitwise operators
* Multiplication
* Subtraction (-)
* Random number inside a range
* Decrementing (--)
* Ceiling and floor
* Math.atan2 to find direction of a vector
* Sin / cos to create a vector given direction distance
* 1Math.hypot
* Periodic functions using Math.sin
* Random with gaussian distribution
* Division
* Getting maximum and minimum
* Restrict Number to Min / Max Range
* Getting roots of a number
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