EN
JavaScript - Math.tan() method example
2
points
Math.tan() is static method that takes only one parameter and returns approximated value of tangent mathematical function.
// 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:
0.9999999999999999,16331239353195370,-0.9999999999999999and-16331239353195370should be equal to1,+Inf,-1and-Infbut 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 as tan(x) mathematical function (primitive value). |
| Description | Math.tan() is static method that takes only one parameter and returns approximated value of tangent mathematical function. |
2. Working with radians
// 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
for (var rad = x1; rad <= x2; rad += dx) {
var y = Math.tan(rad);
console.log('tan(' + rad + ' rad) = ' + y);
}
3. Working with degrees
// ONLINE-RUNNER:browser;
function calculateTan(deg) {
var radians = (Math.PI / 180) * deg;
return Math.tan(radians);
}
// 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);
}
for (var rad = x1; rad < x2; rad += dx) {
var y = Math.tan(rad);
if (y <= y1 || y >= y2) {
console.log(' ');
} else {
printLine(y1, y, '+');
}
}
5. Canvas plot example
// ONLINE-RUNNER:browser;
<!doctype html>
<html>
<head>
<style> #canvas { border: 1px solid black; } </style>
</head>
<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>