Simplify a rational trigonometric expression

The video tutorial explains how to simplify a trigonometric expression involving sine and cosine squared terms. It begins by introducing the problem and then applies trigonometric identities, specifically the Pythagorean identity, to convert sine squared into terms of cosine squared. The instructor demonstrates substitution and simplification techniques, leading to the final simplified expression, which equals one.

Explain the process of substituting sine squared of X in the expression.

What does the final expression equal after simplification?