make atanh and erfc doc-tests pass

Author: LorrensP-2158466

library/std/src/num/f128.rs

@@ -912,10 +912,10 @@ impl f128 {
     /// # #[cfg(not(miri))]
     /// # #[cfg(target_has_reliable_f128_math)] {
     ///
-    /// let e = std::f128::consts::E;
-    /// let f = e.tanh().atanh();
+    /// let x = std::f128::consts::FRAC_PI_6;
+    /// let f = x.tanh().atanh();
     ///
-    /// let abs_difference = (f - e).abs();
+    /// let abs_difference = (f - x).abs();
     ///
     /// assert!(abs_difference <= 1e-5);
     /// # }

library/std/src/num/f16.rs

@@ -877,10 +877,10 @@ impl f16 {
     /// # #[cfg(not(miri))]
     /// # #[cfg(target_has_reliable_f16_math)] {
     ///
-    /// let e = std::f16::consts::E;
-    /// let f = e.tanh().atanh();
+    /// let x = std::f16::consts::FRAC_PI_6;
+    /// let f = x.tanh().atanh();
     ///
-    /// let abs_difference = (f - e).abs();
+    /// let abs_difference = (f - x).abs();
     ///
     /// assert!(abs_difference <= 0.01);
     /// # }

library/std/src/num/f32.rs

@@ -1120,10 +1120,10 @@ impl f32 {
     /// # Examples
     ///
     /// ```
-    /// let e = std::f32::consts::E;
-    /// let f = e.tanh().atanh();
+    /// let x = std::f32::consts::FRAC_PI_6;
+    /// let f = x.tanh().atanh();
     ///
-    /// let abs_difference = (f - e).abs();
+    /// let abs_difference = (f - x).abs();
     ///
     /// assert!(abs_difference <= 1e-5);
     /// ```

library/std/src/num/f64.rs

@@ -1120,10 +1120,10 @@ impl f64 {
     /// # Examples
     ///
     /// ```
-    /// let e = std::f64::consts::E;
-    /// let f = e.tanh().atanh();
+    /// let x = std::f64::consts::FRAC_PI_6;
+    /// let f = x.tanh().atanh();
     ///
-    /// let abs_difference = (f - e).abs();
+    /// let abs_difference = (f - x).abs();
     ///
     /// assert!(abs_difference < 1.0e-10);
     /// ```
@@ -1248,7 +1248,7 @@ impl f64 {
     /// let one = x.erf() + x.erfc();
     /// let abs_difference = (one - 1.0).abs();
     ///
-    /// assert!(abs_difference <= f64::EPSILON);
+    /// assert!(abs_difference <= 1e-10);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]