Hardwire return values for domain limits of arcsin and arccos

fix for issue #7 
#7

Author: CedarGroveStudios

jepler_udecimal/utrig.py

@@ -198,7 +198,13 @@ def asin(x, context=None):
 
     with localcontext(context) as ctx:
         ctx.prec += 2
-        r = atan(x / (1 - x * x).sqrt())
+        pi = Decimal(1).atan() * 4
+        if x == 1:
+            r = pi / 2  # pi * 1/2 radians
+        elif x == -1:
+            r = pi * 3 / 2  # pi * 3/2 radians
+        else:
+            r = atan(x / (1 - x * x).sqrt())
     return r / 1
 
 
@@ -218,10 +224,15 @@ def acos(x, context=None):
 
     with localcontext(context) as ctx:
         ctx.prec += 2
-        r = atan((1 - x * x).sqrt() / x)
+        if x == 1:
+            r = Decimal(0). # 0 radians
+        elif x == -1:
+            r = Decimal(1).atan() * 4  # pi radians
+        else:
+            r = atan((1 - x * x).sqrt() / x)
         if r < 0:
             r += 4 * atan(1)
-        return r
+        return r / 1
 
 
 for name in __all__: