Update darts hints to mention Elixir gotchas (#1434)

* Update hints.md

* Update exercises/practice/darts/.docs/hints.md

Author: jiegillet

exercises/practice/darts/.docs/hints.md

@@ -2,6 +2,6 @@
 
 ## General
 
-- The distance of a point `(x, y)` from the center of the target `(0, 0)` can be calculated with `sqrt(x*x + y *y)`
-
-- You can calculate the square root of `x` by raising it to the power of `1/2`. In other words, `sqrt(x) == pow(x, 0.5)`
+- The distance of a point `(x, y)` from the center of the target `(0, 0)` can be calculated with `sqrt(x * x + y * y)`.
+- Elixir doesn't have a built-in square root function, but the Erlang function `:math.sqrt/1` is available.
+- Alternatively, you can calculate the square root of `x` by raising it to the power of `1/2`. In other words, `def sqrt(x), do: Float.pow(x, 0.5)`. Note that `Float.pow/2` only accepts float arguments, integers need to be converted explicitly, for example with `1.0 * x`.