Problem: For the commercial naming of a product, the frame rate is often dropped and is implied from context (e.g., a 1080i television set). A frame rate can also be specified without a resolution. For example, 24p means 24 progressive scan frames per second, and 50i means 25 interlaced frames per second.
What is usually dropped for the commercial naming of an SDTV product?
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Answer: unanswerable

Problem: The Xinhai Revolution led to the founding of the Republic of China in January 1912 with Sun Yat-sen as the first provisional president and Nanking was selected as its new capital. However, the Qing Empire controlled large regions to the north, so revolutionaries asked Yuan Shikai to replace Sun as president in exchange for the abdication of Puyi, the Last Emperor. Yuan demanded the capital be Beijing (closer to his power base).
When was the Republic of China founded?
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Answer: January 1912

Problem: In general relativity, a vanishing stress-energy tensor implies, through Einstein field equations, the vanishing of all the components of the Ricci tensor. Vacuum does not mean that the curvature of space-time is necessarily flat: the gravitational field can still produce curvature in a vacuum in the form of tidal forces and gravitational waves (technically, these phenomena are the components of the Weyl tensor). The black hole (with zero electric charge) is an elegant example of a region completely "filled" with vacuum, but still showing a strong curvature.
Who's equations helped to imply vanishing of the Ricci tensor?
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Answer:
Einstein