Q.Create a menu driven program using user defined functions to implement a calculator that performs the following:

One user-defined function per operation + a menu loop that dispatches to them; the math module supplies log10, sin, cos.

import math

def add(x, y):      return x + y
def subtract(x, y): return x - y
def multiply(x, y): return x * y
def divide(x, y):
    if y == 0:
        return "Error: division by zero"
    return x / y

while True:
    print("\n1.Add 2.Subtract 3.Multiply 4.Divide 5.log10(x) 6.sin(x) 7.cos(x) 8.Exit")
    ch = int(input("Enter choice: "))
    if ch == 8:
        break
    if ch in (1, 2, 3, 4):
        x = float(input("First number: "))
        y = float(input("Second number: "))
        ops = {1: add, 2: subtract, 3: multiply, 4: divide}
        print("Result =", ops[ch](x, y))
    elif ch == 5:
        print("Result =", math.log10(float(input("x: "))))
    elif ch == 6:
        print("Result =", math.sin(float(input("x (radians): "))))
    elif ch == 7: …

The idea. A menu-driven program is a dispatcher: an endless while loop shows options, reads a choice, and routes to the right function. Writing each operation as its own user-defined function keeps the menu logic and the arithmetic cleanly separated — and part (b) simply reuses ready-made functions from the math module instead of reinventing them.

import math

# --- part (a): basic arithmetic operations -------------------------
def add(x, y):
    return x + y

def subtract(x, y):
    return x - y

def multiply(x, y):
    return x * y

def divide(x, y):
    if y == 0:
        return "Error: division by zero"
    return x / y

# --- the menu loop --------------------------------------------------
while True:
    print()
    print("========  CALCULATOR  ========")
    print("1. Add            5. log10(x)")
    print("2. Subtract       6. sin(x)")
    print("3. Multiply       7. cos(x)")
    print("4. Divide         8. Exit")
    choice = int(input("Enter your choice (1-8): "))

    if choice == 8:
        print("Goodbye!")
        break
    elif choice in (1, 2, 3, 4):
        x = float(input("Enter first number: "))
        y = float(input("Enter second number: "))
        if choice == 1:
            print("Result =", add(x, y))
        elif choice == 2:
            print("Result =", subtract(x, y))
        elif choice == 3:
            print("Result =", multiply(x, y))
        else:
            print("Result =", divide(x, y))
    elif choice in (5, 6, 7):                 # part (b): math functions
        x = float(input("Enter the value of x: "))
        if choice == 5:
            print("Result =", math.log10(x))
        elif choice == 6:
            print("Result =", math.sin(x))
        else:
            print("Result =", math.cos(x))
    else:
        print("Invalid choice — please pick 1 to 8.")

Sample run

========  CALCULATOR  ========
1. Add            5. log10(x)
2. Subtract       6. sin(x)
3. Multiply       7. cos(x)
4. Divide         8. Exit
Enter your choice (1-8): 1
Enter first number: 12
Enter second number: 8
Result = 20.0

Enter your choice (1-8): 5 …