tour: make Newton's method example more straightforward

Change-Id: Ie3473dfcfbd7272d40ff26110261f721f74d026a
Reviewed-on: https://go-review.googlesource.com/33930
Reviewed-by: Jaana Burcu Dogan <jbd@google.com>

1 files changed, 9 insertions, 5 deletions

diff --git a/content/flowcontrol.article b/content/flowcontrol.article
index 4adfb65..9720b34 100644
--- a/content/flowcontrol.article
+++ b/content/flowcontrol.article
@@ -73,17 +73,21 @@ in `main` begins.)
 
 * Exercise: Loops and Functions
 
-As a simple way to play with functions and loops, implement the square root function using Newton's method.
+As a way to play with functions and loops, implement the square root function using Newton's method.
 
-In this case, Newton's method is to approximate `Sqrt(x)` by picking a starting point _z_ and then repeating:
+Newton's method is to approximate `Sqrt(x)` by picking a starting point _z_ first, and repeating:
 
 .image /content/img/newton.png
 
-To begin with, just repeat that calculation 10 times and see how close you get to the answer for various values (1, 2, 3, ...).
+Hint: Iterate and return the final value of _z_ as the answer:
 
-Next, change the loop condition to stop once the value has stopped changing (or only changes by a very small delta). See if that's more or fewer iterations. How close are you to the [[https://golang.org/pkg/math/#Sqrt][math.Sqrt]]?
+	z -= (z*z - x) / (2*z)
 
-Hint: to declare and initialize a floating point value, give it floating point syntax or use a conversion:
+To begin with, repeat the calculation 10 times and see how close you get to the answer for various values (1, 2, 3, ...).
+
+Next, change the loop condition to stop once the value has stopped changing (or only changes by a very small amount). See if that's more or fewer than 10 iterations. How close are you to the [[https://golang.org/pkg/math/#Sqrt][math.Sqrt]]?
+
+Hint: To declare and initialize a floating point value, give it floating point syntax or use a conversion:
 
 	z := float64(1)
 	z := 1.0