35mm Format?

Thanks!

oops,
the ratio your instructor used so inappropriately is the golden mean

"The Golden Mean is a ratio that is present in the growth patterns of many things--the spiral formed by a shell or the curve of a fern, for example. The Golden Mean or Golden Section was derived by the ancient Greeks. Like "pi", the number 1.618... is an irrational number. Both the ancient Greeks and the ancient Egyptians used the Golden Mean when designing their buildings and monuments. The builders of Paestum used the Golden Mean in their temples. Artists as diverse as Leonardo da Vinci and George Seurat used the ratio when constructing their paintings. These artists and architects discovered that by utilizing the ratio 1 : 1.618..., they could create a feeling of order in their works. Even today, artists are still using this proportion in their works, and scientists, like Roger Penrose are discovering new things about the Golden Mean and its place in science, mathematics, and nature."
(this definition was taken from the first URL that came up in a Google search.)

As noted by others, the format ratios used by various cameras have nothing to do with the golden mean. It is a compositional element that can be used within any camera format. For example the focal point of a composition can be placed in a square image based on the golden mean. The horizon can be placed in a 35mm or 4X5 image based on the golden mean, etc.

In advancing your photographic education study the compositional use of the golden mean as well as other "tricks" that have been utilized by artists since the dawn of image making.

David