What are the products of numerators and opposite denominators in a proportion

Astudent simplified a rational expression as shown.

Television sizes are based on the length of the diagonal of the television's rectangular screen. so, for example, a 70-inch television is a television having a diagonal screen length of 70 inches. if a 70 inch television's diagonal forms a 29°angle with the base of the screen, what is the vertical height (1) of the screen to the nearest inch? 70 inhin

If a || b and e || f , what if the value of y ?