permutation and combination called

src/main/c/Calculator/calculator.c

@@ -250,3 +250,14 @@ double cosine(double angle) {
 double tangent(double angle) {
     return tan(angle * M_PI / 180.0);
 }
+double permutation(int n, int r) {
+    int result = 1;
+    for (int i = 0; i < r; i++) {
+        result *= (n - i);
+    }
+    return result;
+}
+
+double combination(int n, int r) {
+    return permutation(n, r) / factorial(r);
+}