user: I'm working on some mathematical problems and need to do a couple of calculations. First, I need to figure out the greatest common divisor (GCD) for the numbers 36 and 48. After that, I need to estimate the derivative of the function f(x) = x^2 at the point where x equals 5. Can you help me with these two tasks?

Available functions:
name: math_gcd
description: Calculates the greatest common divisor of two numbers.
parameters: type: dict
properties: a: type: integer
description: The first number. This should be the larger number.
b: type: integer
description: The second number.
required: a
b
name: estimate_derivative
description: Estimate the derivative of a function at a given point.
parameters: type: dict
properties: function: type: string
description: The function to calculate the derivative of.
x: type: integer
description: The point to calculate the derivative at.
required: function
x