fix code formatting for including headers (#153)

Fix code formatting for including headers

diff --git a/doc/docs/NLopt_Tutorial.md b/doc/docs/NLopt_Tutorial.md
index faf9d1bb933624f94630f9830ba6cdd3d0453431..b86e8f97c89a22eb458137de8441c6a2ec6fdee6 100644 (file)
--- a/doc/docs/NLopt_Tutorial.md
+++ b/doc/docs/NLopt_Tutorial.md
@@ -32,8 +32,10 @@ Example in C/C++
 
 To implement the above example in C or C++, we would first do:
 
-`#include `<math.h>
-`#include `<nlopt.h>
+```c
+#include <math.h>
+#include <nlopt.h>
+```
 
 to include the NLopt header file as well as the standard math header file (needed for things like the `sqrt` function and the `HUGE_VAL` constant), then we would define our objective function as: