# p5.js | atan() Function

• Last Updated : 06 Sep, 2019

The atan() function in p5.js is used to calculate the inverse of tan() or arc tangent of a value ranging in between -Infinity to Infinity (exclusive) and gives result in the range of -π/2 to π/2.

Syntax:

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`atan(P)`

Parameters: This function accepts a parameter “P” which is a value ranging from -1 to 1 and whose arc tangent is calculated.

Return Value: It returns the arc tangent of a value and its range is in between -π/2 to π/2.

Below program illustrates the atan() function in p5.js:

Example: This example uses atan() function to get arc tangent of a value.

 `function` `setup() { `` ` `    ``// Create Canvas of size 270*80 ``    ``createCanvas(550, 130); ``} `` ` `function` `draw() { ``     ` `    ``// Set the background color ``    ``background(220); ``     ` `    ``// Initialize the parameter with some values``    ``let a = 0; ``    ``let b = 88; ``        ``let c = -1;``        ``let d = -0.5;``        ``let e = 5;``     ` `    ``// Call to atan() function ``    ``let v = atan(a);``        ``let w = atan(b);``        ``let x = atan(c);``        ``let y = atan(d);``        ``let z = atan(e);``     ` `    ``// Set the size of text ``    ``textSize(16); ``     ` `    ``// Set the text color ``    ``fill(color(``'red'``)); ``   ` `    ``// Getting arc tangent value ``    ``text(``"Arc tangent value of 0 is : "` `+ v, 50, 30);``        ``text(``"Arc tangent value of 88 is : "` `+ w, 50, 50);``        ``text(``"Arc tangent value of -1 is : "` `+ x, 50, 70);``        ``text(``"Arc tangent value of -0.5 is : "` `+ y, 50, 90);``        ``text(``"Arc tangent value of 5 is : "` `+ z, 50, 110);     ``} `

Output: Reference: https://p5js.org/reference/#/p5/atan

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