add functions

src/functions/functions.py

+import math
+
+
+def fn_sin(x: float) -> float:
+    return math.sin(x)
+
+
+def fn_cos(x: float) -> float:
+    return math.cos(x)
+
+
+def fn_ln(x: float) -> float:
+    return math.log(x)
+
+
+def fn_sqrt(x: float) -> float:
+    return math.sqrt(x)
+
+
+def fn_square(x: float) -> float:
+    return x ** 2
+
+
+def fn_cube(x: float) -> float:
+    return x ** 3