fix: Set default angle mode to degrees and simplify error messages

calculator/calculator.app.js

@@ -64,7 +64,7 @@ var scientificOperators = {
   'sin': {grid: [0, 0], val: 'sin'},
   'cos': {grid: [1, 0], val: 'cos'},
   'tan': {grid: [0, 1], val: 'tan'},
-  'angleMode': {grid: [1, 1], val: 'rad'},
+  'angleMode': {grid: [1, 1], val: 'deg'},
   'log': {grid: [0, 2], val: 'log'},
   'tenpow': {grid: [1, 2], val: '10^x'},
   'ln': {grid: [0, 3], val: 'ln'},
@@ -86,7 +86,7 @@ var operator = null;
 var results = null;
 var isDecimal = false;
 var hasPressedEquals = false;
-var angleMode = 'rad';
+var angleMode = 'deg';
 
 function prepareScreen(screen, grid, defaultColor) {
   for (var k in screen) {
@@ -225,11 +225,11 @@ function displayOutput(num) {
   if (num === Infinity || num === -Infinity || isNaN(num)) {
     // handle division by 0
     if (num === Infinity) {
-      num = 'INFINITY';
+      num = 'INF';
     } else if (num === -Infinity) {
-      num = '-INFINITY';
+      num = '-INF';
     } else {
-      num = 'NOT A NUMBER';
+      num = 'NaN';
     }
     currNumber = null;
     results = null;