Editorial: fix algorithm of Math.atan2 (#3170)

spec.html

@@ -31937,7 +31937,13 @@ <h1>Math.atan2 ( _y_, _x_ )</h1>
             1. If _nx_ is *-∞*<sub>𝔽</sub>, return an implementation-approximated Number value representing -π.
             1. If _nx_ is either *+0*<sub>𝔽</sub> or *-0*<sub>𝔽</sub>, return an implementation-approximated Number value representing -π / 2.
           1. Assert: _nx_ is finite and is neither *+0*<sub>𝔽</sub> nor *-0*<sub>𝔽</sub>.
-          1. Return an implementation-approximated Number value representing the result of the inverse tangent of the quotient ℝ(_ny_) / ℝ(_nx_).
+          1. Let _r_ be the inverse tangent of abs(ℝ(_ny_) / ℝ(_nx_)).
+          1. If _nx_ &lt; *-0*<sub>𝔽</sub>, then
+            1. If _ny_ > *+0*<sub>𝔽</sub>, set _r_ to π - _r_.
+            1. Else, set _r_ to -π + _r_.
+          1. Else,
+            1. If _ny_ &lt; *-0*<sub>𝔽</sub>, set _r_ to -_r_.
+          1. Return an implementation-approximated Number value representing _r_.
         </emu-alg>
       </emu-clause>