add recipe on exponents and logarithms

Author: jlburkhead

chapters/math/working-with-exponents-and-logarithms.md

@@ -0,0 +1,37 @@
+---
+layout: recipe
+title: Working with Exponents and Logarithms
+chapter: Math
+---
+## Problem
+
+You need to do some calculations that involve exponents and logarithms.
+
+## Solution
+
+Use Javascript's Math object to provide common mathematical functions.
+
+{% highlight coffeescript %}
+# Math.pow(x, y) returns x^y
+Math.pow(2, 4)
+# => 16
+
+# Math.exp(x) returns E^x and is shorthand for Math.pow(Math.E, x)
+Math.exp(2)
+# => 7.38905609893065
+
+# Math.log returns the natural (base E) log
+Math.log(5)
+# => 1.6094379124341003
+Math.log(Math.exp(42))
+# => 42
+
+# To get a log with some other base n, divide by Math.log(n)
+Math.log(100) / Math.log(10)
+# => 2
+
+{% endhighlight %}
+
+## Discussion
+
+For more information on the Math object see the documentation on the [Mozilla Developer Netword](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math). Also refer to [Converting Radians and Degrees](/chapters/math/radians-degrees) for discussion of the various constants in the Math object.