The image contains a mathematical expression. Please provide the expression in a parsable JSON format, and also in a plain text format.

Mathematical Expression:

The mathematical expression from the image is:

\[ \log_2 \left( \sqrt{\frac{a^2 - b^2}{a^2 + b^2}} \right) \]

Plain Text Representation:

log_2(sqrt((a^2 - b^2) / (a^2 + b^2)))