Solve bug with parenthesis and ^

pymath/calculus/operator/pw.py

@@ -19,7 +19,7 @@ class Pw(Operator):
     >>> pw.__tex__('2','-3')
     '2^{  -3 }'
     >>> pw.__tex__('-2','3')
-    '( -2 )^{  -3 }'
+    '( -2 )^{  3 }'
     >>> pw.__txt__('2','3')
     '2 ^ 3'
     >>> pw.__txt__('-2','3')
@@ -66,6 +66,19 @@ class Pw(Operator):
             ans = ' '.join([str(i) for i in ans])
         return ans
 
+    def __tex__(self, *args):
+        """Tex rendering for ^
+
+        :*args: Operands for this operation
+        :returns: String with operator and his operands
+
+        """
+        op1 = self.l_parenthesis(args[0], True)
+        op2 = args[1]
+        ans = self.tex.format(op1 = op1, op2 = op2)
+
+        return ans
+
 
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