# 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:

`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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