First and Second Derivatives with Taylor Expansions
1. First and Second Derivatives The first derivative of a function f(x), denoted f'(x), measures the rate of change of f(x) with respect to x. It tells us whether the function is increasing or decreasing at a given point. The second derivative, f''(x), measures the rate of change of the first derivative. It tells us about the concavity of the function (whether it's curving upward or downward) and helps identify points of inflection. Example: Consider f(x) = x^2. - First derivative: f'(x) = 2x. This tells us that the slope of f(x) at any point x is 2x. - Second derivative: f''(x) = 2. Since f''(x) > 0, the function is concave upward everywhere. --- 2. Taylor Expansions A Taylor expansion approximates a function f(x) near a point x = a using its derivatives. The idea is to express f(x) as a polynomial, which is easier to work with. The Taylor seriesof f(x) around x = a is: f(x) = f(a) + f'(a) (x - a) + (f''(a) / 2!) (x - a)^2 + (f'...