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# JavaScript - Math.tan() method example

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`Math.tan()`Â is static method that takes only one parameter and returnsÂ approximated valueÂ of tangent mathematical function.Â

``````// ONLINE-RUNNER:browser;

console.log( Math.tan( 0                  ) ); //     0 <-    0 degrees
console.log( Math.tan( 0.7853981633974483 ) ); //    ~1 <-  ~45 degrees ==  PI / 4
console.log( Math.tan( 1.5707963267948966 ) ); // ~+Inf <-  ~90 degrees ==  PI / 2

console.log( Math.tan(-0.7853981633974483 ) ); //   ~-1 <- ~-45 degrees == -PI / 4
console.log( Math.tan(-1.5707963267948966 ) ); // ~-Inf <- ~-90 degrees == -PI / 2``````

Note:Â `0.9999999999999999`, `16331239353195370`, `-0.9999999999999999` and `-16331239353195370`Â should be equal to `1`,Â `+Inf`, `-1` and `-Inf`Â but they are not because of compuptation precision error.

## 1. Documentation

 Syntax `Math.tan(number)` Parameters `number` - integer or float number value in radians (primitive value). Result `number` value calculated asÂ `tan(x)`Â mathematical function (primitive value). Description `Math.tan()`Â is static method that takes only one parameter and returnsÂ approximated value of tangent mathematical function.

``````// ONLINE-RUNNER:browser;

var x1 = 0.0;          // beginning of calculation in radians
var x2 = Math.PI / 2;  // ending of calculation radians

var dx = Math.PI / 36; // calculation step in degrees

}``````

## 3. Working with degrees

``````// ONLINE-RUNNER:browser;

function calculateTan(deg) {
var radians = (Math.PI / 180) * deg;

}

// Example:

var x1 = 0.0;  // beginning of calculation in degrees
var x2 = 90.0; // ending of calculation degrees

var dx = 5.0;  // calculation step in degrees

for (var deg = x1; deg  <= x2; deg  += dx) {
var y = calculateTan(deg );

console.log('tan(' + deg + ' deg) = ' + y);
}``````

## 4. Reversed console plot example

``````// ONLINE-RUNNER:browser;

var x1 = -3.14 * 2; // beginning of sine chart
var x2 = +3.14 * 2; // end of sine chart

var y1 = -4.0;
var y2 = +4.0;

var xSteps = 60;
var ySteps = 60;

var dx = (x2 - x1) / xSteps; // x axis step
var dy = (y2 - y1) / ySteps; // y axis step

function printLine(y1, y2, character) {
var line = '';

for(var y = y1; y < y2; y += dy) {
line += ' ';
}

console.log(line + character);
}

if (y <= y1 || y >= y2) {
console.log(' ');
} else {
printLine(y1, y, '+');
}
}``````

## 5. Canvas plot example

``````// ONLINE-RUNNER:browser;

<!doctype html>
<html>
<style> #canvas { border: 1px solid black; } </style>
<body>
<canvas id="canvas" width="150" height="400"></canvas>
<script>

var canvas = document.querySelector('#canvas');
var context = canvas.getContext('2d');

// tangent chart range
var x1 = -Math.PI / 2; // -90 degress
var x2 = +Math.PI / 2; // +90 degress
var y1 = -10.0;
var y2 = +10.0;

var dx = 0.05;

var xRange = x2 - x1;
var yRange = y2 - y1;

var yScale = 1.0;

function calculatePoint(x) {
var y = Math.tan(x) * yScale;

// chart will be reversed horizontaly because of reversed canvas pixels

var nx = (x - x1) / xRange;       // normalized x
var ny = 1.0 - (y - y1) / yRange; // normalized y

var point = {
x: nx * canvas.width,
y: ny * canvas.height
};

return point;
}

console.log('x range: <' + x1 + '; ' + x2 + '> // angles in radians');
console.log('y range: <' + y1 + '; ' + y2 + '>');

var point = calculatePoint(x1);

context.beginPath();
context.moveTo(point.x, point.y);

for (var x = x1 + dx; x < x2; x += dx) {
point = calculatePoint(x);
context.lineTo(point.x, point.y);
}

point = calculatePoint(x2);
context.lineTo(point.x, point.y);
context.stroke();

</script>
</body>
</html>``````

## References

1. Trigonometric functions - Wikipedia

## Alternative titles

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