12.2 exercise 15

To evaluate the limit of the function \(\frac{x^2 - y^2}{x^2 + y^2}\) as \((x, y)\) approaches \((0, 0)\) along different paths, we will look at two specific paths:

(a) Along the path \(y = 0\)

When \(y = 0\), the function simplifies as follows: \[ \frac{x^2 - y^2}{x^2 + y^2} = \frac{x^2 - 0^2}{x^2 + 0^2} = \frac{x^2}{x^2} = 1 \]

So, along the path \(y = 0\), as \((x, y) \to (0, 0)\), the limit of the function is 1: \[ \lim_{(x, 0) \to (0, 0)} \frac{x^2 - 0^2}{x^2 + 0^2} = 1 \]

(b) Along the path \(x = 0\)

When \(x = 0\), the function simplifies as follows: \[ \frac{x^2 - y^2}{x^2 + y^2} = \frac{0^2 - y^2}{0^2 + y^2} = \frac{-y^2}{y^2} = -1 \]

So, along the path \(x = 0\), as \((x, y) \to (0, 0)\), the limit of the function is -1: \[ \lim_{(0, y) \to (0, 0)} \frac{0^2 - y^2}{0^2 + y^2} = -1 \]

The evaluation along these two paths yields different results:

  • Along \(y = 0\), the limit is 1.
  • Along \(x = 0\), the limit is -1.

Issues

I struggled initially with understanding path-dependent limits, but overcame this through research and reading.

Key takeaway of the course

The key takeaway from the course was understanding how diverse mathematical areas like probability, calculus, algebra, and linear regression converge to serve data science effectively. A particularly interesting example was the application of linear algebra in creating eigenimages for image compression. The final project really brought it all together, demonstrating the vital role of math in data science.