Surface area of a cone The lateral surface area of a cone of radius r and height h (the surface area excluding the base) is A = πr√r²+h².
b. Evaluate this derivative when r=30 and h=40.

Verified step by step guidance

1. First, identify the formula for the lateral surface area of a cone, which is given as A = πr√(r² + h²).
2. To find the derivative of A with respect to r, apply the chain rule. The expression inside the square root, r² + h², is a function of r, so differentiate it with respect to r.
3. The derivative of r² with respect to r is 2r, and since h is a constant, the derivative of h² with respect to r is 0. Therefore, the derivative of r² + h² with respect to r is 2r.
4. Now, differentiate the entire expression A = πr√(r² + h²) with respect to r. Use the product rule, which states that the derivative of a product u*v is u'v + uv'. Here, u = πr and v = √(r² + h²).
5. Evaluate the derivative at r = 30 and h = 40 by substituting these values into the derivative expression obtained in the previous step.

Key Concepts

Lateral Surface Area of a Cone

The lateral surface area of a cone is the area of the cone's curved surface, excluding the base. It is calculated using the formula A = πr√(r² + h²), where r is the radius and h is the height of the cone. This formula derives from the geometry of the cone and involves the Pythagorean theorem to account for the slant height.

Derivative

A derivative represents the rate of change of a function with respect to a variable. In this context, it helps determine how the lateral surface area A changes as the radius r varies, while keeping the height h constant. The derivative is calculated using differentiation rules, which provide insights into the behavior of the function at specific points.

Evaluation of Derivatives

Evaluating a derivative involves substituting specific values into the derivative function to find the instantaneous rate of change at those points. In this case, after finding the derivative of the lateral surface area with respect to r, we will substitute r = 30 and h = 40 to compute the exact rate of change of the surface area at that radius.