use a function-call example for coercing an apparent int to a float. ref #27

examples/constants/constants.go

@@ -4,6 +4,7 @@
 package main
 
 import "fmt"
+import "math"
 
 // `const` declares a constant value.
 const s string = "constant"
@@ -18,15 +19,15 @@ func main() {
     // Constant expressions perform arithmetic with
     // arbitrary precision.
     const d = 3e20 / n
+    fmt.Println(d)
 
     // A numeric constant has no type until it's given
     // one, such as by an explicit cast.
     fmt.Println(int64(d))
 
-    // A number can also be given a type by using it in a
+    // A number can be given a type by using it in a
     // context that requires one, such as a variable
-    // assignment or function call. The type it gets
+    // assignment or function call. For example, here
-    // depends on its value.
+    // `math.Sin` expects a `float64`.
-    fmt.Println(n) // int
+    fmt.Println(math.Sin(n))
-    fmt.Println(d) // float64
 }