Add isgreater() documentation entry for C++ (#7998)

* Create isgreater.md

* Create isgreater.md

* Delete content/cpp/concepts/math-functions  directory

* minor content fixes

* Update isgreater.md

* Update isgreater.md

* Update isgreater.md

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Author: kentgabmagbuhat-oss

content/cpp/concepts/math-functions/terms/isgreater/isgreater.md

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+---
+Title: 'isgreater()'
+Description: 'Compares two floating-point values and returns true if the first is strictly greater than the second.'
+Subjects:
+  - 'Computer Science'
+  - 'Data Science'
+  - 'Game Development'
+Tags:
+  - 'Functions'
+  - 'Comparison'
+  - 'Math'
+CatalogContent:
+  - 'learn-c-plus-plus'
+  - 'paths/computer-science'
+---
+
+The **`isgreater()`** [function](https://www.codecademy.com/resources/docs/cpp/functions) compares two floating-point values and returns `true` only when the first is strictly greater than the second. It follows IEEE-754 rules, never raises floating-point exceptions, and always returns `false` if either argument is `NaN`. Integer inputs are promoted to floating-point. The function is available through the `<cmath>` header.
+
+## Syntax
+
+```pseudo
+isgreater(x, y)
+```
+
+**Parameters:**
+
+- `x`, `y`: Arithmetic values (integers or floating-point types).
+
+> **Note:** Integer arguments are promoted to the appropriate floating-point type.
+
+**Return value:**
+
+The `isgreater()` function returns:
+
+- `true` if `x > y` and neither argument is `NaN`
+- `false` otherwise, including when either value is `NaN`
+
+## Example
+
+The following example checks whether one number is greater than another, including a comparison involving `NaN`:
+
+```cpp
+#include <iostream>
+#include <iostream>
+#include <cmath>
+
+using namespace std;
+
+int main() {
+  double x = 10.5;
+  double y = 5.2;
+  double z = nan("1");
+
+  cout << boolalpha;
+  cout << "isgreater(x, y): " << isgreater(x, y) << endl;
+  cout << "isgreater(x, z): " << isgreater(x, z) << " (NaN comparison)" << endl;
+
+  return 0;
+}
+```
+
+The output of this code is as follows:
+
+```shell
+isgreater(x, y): true
+isgreater(x, z): false (NaN comparison)
+```
+
+## Codebyte Example
+
+The following example is runnable and outputs whether one number is greater than another using `isgreater()`:
+
+```codebyte/cpp
+#include <iostream>
+#include <cmath>
+using namespace std;
+
+int main() {
+  double a = 7.5;
+  double b = 9.3;
+
+  cout << boolalpha;
+  cout << "isgreater(a, b): " << isgreater(a, b) << endl;
+  cout << "isgreater(b, a): " << isgreater(b, a) << endl;
+
+  return 0;
+}
+```