 # The JavaScript Diaries: Part 14

The `Math` object is a predefined JavaScript object used to perform mathematical operations. It's also used to obtain the values of predefined mathematical constants, i.e., Pi (`π`) or the square root of a number. In addition, it can also be used to generate random numbers.

It's important to remember that the `Math` object begins with an uppercase "M." If a lower case "m" is used, the JavaScript interpreter will not recognize it as an object.

(Note: We won't cover all of these properties and methods in detail as some of them are a little more complicated than what we are dealing with right now.)

### Properties

 Name Description E The value of Euler's constant, approximately 2.718 LN2 The natural logarithm of 2, approximately 0.693 LN10 The natural logarithm of 10, approximately 2.302 LOG2E The base 2 logarithm of E, approximately 1.442 LOG10E The base 10 logarithm of E, approximately 0.434 PI (`π`) The ratio of the circumference of a circle to its diameter, approximately 3.14159 SQRT1_2 Square root of 1/2; equivalently, 1 over the square root of 2, approximately 0.707 SQRT2 Square root of 2, approximately 1.414

#### Using Pi

You can use this script to calculate the circumference of a circle using Pi by entering the radius:

Let's see what we did in this script.

 First, we created a function called `circum`. Then, we declared the variable `radius` and gave it the value of the results of a `prompt` box, which obtains the size of the radius from the user. Next, we declared the variable `circle` and gave it the formula which will calculate the actual circumference of the circle, based on the information given to the `radius` variable. Finally, an `alert` box displays the results of the calculation.

You would then add this in the `body` section of the page in order to call the script above:

Let's take a look at the JavaScript math methods and see what we can do with them.

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