Macrumors- According to new information from the China Times translated by BrightWire, Apple is planning to release the iPhone 5S alongside a larger phone, deemed the "iPhone Math" by the report.
Because the iPhone Math name is highly unusual and does not fit in with Apple's traditional naming scheme, it is not clear if it is a code name or a potential mistranslation, although the actual "iPhone Math" terms appears in English in the China Times report.

