exercise 2.6: anonymous function for beta

02-basicfunctions/exercises/ex2.6

@@ -0,0 +1,12 @@
+Anonymous function definition is:
+
+```
+\x -> 1 / sqrt(1 - x^2)
+```
+
+Sample application to 0.8 is:
+
+```
+(\x -> 1 / sqrt(1 - x^2)) 0.8
+1.666666666666667
+```