Java Script Math.tan Method
By Stephen Bucaro
Tangent is a trigonometric function. Based on a right triangle. It's the ratio of the
length of the opposite side to the length of the adjacent side.
Tangent A = opposite/adjacent
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 tangent of the angle to calculate the length of the opposite side.
length of opposite = length of adjacent * tangent of angle
Example
angle = 35 degrees
adjacent side = 10
Java Script Using Math.tan Method
<script type="text/javascript">
var angle = 35;
var adjacent = 10;
var opposite = adjacent * Math.tan(35 * Math.PI/180);
alert(opposite.toFixed(3));
</script>
The code shown above uses the Java Script Math.tan method. The Math.tan 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:
• Java Script Reserved Words
• Window Object Properties and Methods
• Java Script prompt Message Box
• Access Web Page Elements With getElementById
• Java Script Trigonometric Methods
• Format a Number as Currency
• A Brief History of JavaScript
• The switch / case Structure
• JavaScript Operators
• Java Script alert Message Box
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