Java Script Math.cos Method
By Stephen Bucaro
Cosine is a trigonometric function. Based on a right triangle. It's the ratio of the
length of the adjacent side to the length of the hypotenuse.
cosine A = adjacent/hypotenuse
In identifying the sides of a right triangle, the side next to the angle for which we
are using the trigonometric function is called the adjacent side. The side opposite that
angle is called the opposite side.
If you know an angle and the length of the side adjacent to the angle, you can
use the cosine of the angle to calculate the length of the hypotenuse.
length of hypotenuse = length of adjacent/cosine of angle
Example
angle = 35 degrees
opposite side = 8
Java Script Using Math.cos Method
<script type="text/javascript">
var angle = 35;
var adjacent = 8;
var hypotenuse = adjacent/Math.cos(35 * Math.PI/180);
alert(hypotenuse.toFixed(3));
</script>
The code shown above uses the Java Script Math.cos method. The Math.cos method requires
the angle passed to it to be in radians. A radian is the angle of an arc created by
wrapping the radius of a circle around its circumference. It sounds like a weard unit, by
by coincidence there are 2 PI radians in a complete circle. This makes this much easier in
fields like calculus. To convert degrees to radians, multiply by PI/180.
The code shown above also uses the Number objects .toFixed(n) method. This method
converts a value to a number with n digits to the right of the decimal point.
More Java Script Code: • Rounding a Number with JavaScript • Comparison Operators • Java Script Math.sin Method • Java Script Number Object • Format a Number as Currency • The continue Statement • Determine Absolute Value • Using the Java Script eval() Function • The Location Object • Java Script Math.tan Method
