Math Problem Statement

Expand f (x,y) = e^-x logy upto second degree

Solution

To expand the function f(x,y)=exlog(y)f(x, y) = e^{-x} \log(y) up to the second degree, we need to use a Taylor series expansion around a point, typically (x0,y0)(x_0, y_0). Let’s assume we expand around the point (x0=0,y0=1)(x_0 = 0, y_0 = 1), which is a common choice for logarithmic functions.

The general form of the second-degree Taylor expansion for a function of two variables f(x,y)f(x, y) around (x0,y0)(x_0, y_0) is:

f(x,y)f(x0,y0)+(xx0)fx(x0,y0)+(yy0)fy(x0,y0)+12((xx0)22fx2(x0,y0)+2(xx0)(yy0)2fxy(x0,y0)+(yy0)22fy2(x0,y0))f(x, y) \approx f(x_0, y_0) + (x - x_0) \frac{\partial f}{\partial x} \bigg|_{(x_0, y_0)} + (y - y_0) \frac{\partial f}{\partial y} \bigg|_{(x_0, y_0)} + \frac{1}{2} \left( (x - x_0)^2 \frac{\partial^2 f}{\partial x^2} \bigg|_{(x_0, y_0)} + 2(x - x_0)(y - y_0) \frac{\partial^2 f}{\partial x \partial y} \bigg|_{(x_0, y_0)} + (y - y_0)^2 \frac{\partial^2 f}{\partial y^2} \bigg|_{(x_0, y_0)} \right)

Step 1: Calculate f(x0,y0)f(x_0, y_0)

f(0,1)=e0log(1)=10=0f(0, 1) = e^0 \log(1) = 1 \cdot 0 = 0

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Multivariable Calculus
Taylor Series
Logarithmic Functions

Formulas

f(x, y) ≈ f(x_0, y_0) + (x - x_0) ∂f/∂x |_(x_0, y_0) + (y - y_0) ∂f/∂y |_(x_0, y_0) + 1/2 [ (x - x_0)^2 ∂²f/∂x² |_(x_0, y_0) + 2(x - x_0)(y - y_0) ∂²f/∂x∂y |_(x_0, y_0) + (y - y_0)^2 ∂²f/∂y² |_(x_0, y_0)]
f(x, y) = e^(-x) log(y)

Theorems

Taylor Series Expansion

Suitable Grade Level

Undergraduate Calculus