EN
JavaScript - Math.cos() method example
15 points
The Math.cos() function returns the cosine of the specified angle in radians in the range -1 to +1.
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console.log( Math.cos( 0 ) ); // 1 <- 0 degrees2
console.log( Math.cos( 1.5707963267948966 ) ); // ~0 <- ~90 degrees == PI / 23
console.log( Math.cos( 3.1415926535897932 ) ); // ~-1 <- ~180 degrees == PI4
console.log( Math.cos( 4.71238898038469 ) ); // ~0 <- ~270 degrees == -PI * (3 / 2)5
console.log( Math.cos( 6.2831853071795850 ) ); // ~1 <- ~360 degrees == PI * 26
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console.log( Math.cos(-1.5707963267948966 ) ); // ~0 <- ~-90 degrees == -PI / 2Note:
6.123233995736766e-17,-1.8369701987210297e-16and6.123233995736766e-17should be equal to0but they are not because of computation precision error.
| Syntax | Math.cos(number) |
| Parameters | number - integer or float number value in radians (primitive value). |
| Result |
returns a numeric value between |
| Description | cos is static method that takes only one parameter and returns approximation of cos(x) mathematical function result. |
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var x1 = 0.0; // beginning of calculation in radians2
var x2 = Math.PI / 2; // ending of calculation radians3
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var dx = Math.PI / 36; // calculation step in degrees5
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for (var rad = x1; rad <= x2; rad += dx) {7
var y = Math.cos(rad);8
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console.log('cos(' + rad + ' rad) = ' + y);10
}xxxxxxxxxx1
function calculateCos(deg) {2
var rad = (Math.PI / 180) * deg;3
return Math.cos(rad);4
}5
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// Usage example:8
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var x1 = 0.0; // beginning of calculation in degrees10
var x2 = 90.0; // ending of calculation degrees11
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var dx = 5.0; // calculation step in degrees13
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for (var deg = x1; deg <= x2; deg += dx) {15
var y = calculateCos(deg );16
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console.log('cos(' + deg + ' deg) = ' + y);18
}xxxxxxxxxx1
var x1 = 0.0; // beginning of cosine chart2
var x2 = 6 * 3.14 // end of cosine chart3
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var dx = 3.14 / 4.0; // x axis step5
var dy = 1.0 / 5.0; // y axis step6
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for (var rad = x1; rad < x2; rad += dx) {8
var y1 = 0.0;9
var y2 = Math.cos(rad) + 1;10
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var line = '';12
for(var y = y1; y < y2; y += dy) {13
line += ' ';14
}15
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console.log(line + '+');17
}xxxxxxxxxx1
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<html>3
<head>4
<style> #canvas { border: 1px solid black; } </style>5
</head>6
<body>7
<canvas id="canvas" width="400" height="130"></canvas>8
<script>9
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function Chart(canvas, x1, x2, y1, y2, dx, func) {11
var self = this;12
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var context = canvas.getContext('2d');14
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var width = canvas.width;16
var height = canvas.height;17
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var xRange = x2 - x1;19
var yRange = y2 - y1;20
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var calculatePoint = function(x) {22
var y = func(x);23
// chart will be reversed horizontaly because of reversed canvas pixels24
var nx = (x - x1) / xRange; // normalized x25
var ny = 1.0 - (y - y1) / yRange; // normalized y26
return {27
x: nx * width,28
y: ny * height29
};30
};31
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self.drawChart = function() {33
var point = calculatePoint(x1);34
context.beginPath();35
context.moveTo(point.x, point.y);36
for (var x = x1 + dx; x < x2; x += dx) {37
var point = calculatePoint(x);38
context.lineTo(point.x, point.y);39
}40
var point = calculatePoint(x2);41
context.lineTo(point.x, point.y);42
context.stroke();43
};44
};45
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// Usage example:48
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var canvas = document.querySelector('#canvas');50
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// cosine chart range52
var x1 = 0; // 0 degress53
var x2 = +2 * Math.PI; // +360 degress54
var y1 = -1.0;55
var y2 = +1.0;56
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var dx = 0.1;58
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var chart = new Chart(canvas, x1, x2, y1, y2, dx, Math.cos);60
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chart.drawChart();62
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console.log('x range: <' + x1 + '; ' + x2 + '> // angles in radians');64
console.log('y range: <' + y1 + '; ' + y2 + '>');65
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</script>67
</body>68
</html>