Seen here is the Norwich City Council’s first computer, being delivered to the City Treasurer’s Department in Bethel Street, Norwich in 1957. The City of Norwich, and its forward-thinking Treasurer, Mr A.J. Barnard, were pioneers in the application of computer technology to the work of UK local authorities and businesses. In 1953-4, Mr Barnard and his team began looking for an electronic system to handle its rates and payroll. They began discussions with Elliott Brothers of London in 1955, and the City Council ordered the first Elliott 405 computer from them in January 1956. It was delivered to City Hall in February 1957 and became operational in April 1957. The event was celebrated by a demonstration of the machine in front of the Lord Mayor of Norwich and the press on 3 April 1957. (Norfolk Record Office, ACC 2005/170)
Below is a picture of the new $5 Raspberry Pi Zero at the same location. The Raspberry Pi is a tiny and affordable computer, designed and built in the UK, that you can use to learn programming through fun, practical projects. I own 2 older models.
Proof by cumbersome notation The theorem follows immediately from the fact that when .
Proof by inaccessible literature The theorem is an easy corollary of a result proven in a hand-written note handed out during a lecture by the Yugoslavian Mathematical Society in 1973.
Proof by ghost reference The proof my be found on page 478 in a textbook which turns out to have 396 pages.
Circular argument Proposition 5.18 in [BL] is an easy corollary of Theorem 7.18 in [C], which is again based on Corollary 2.14 in [K]. This, on the other hand, is derived with reference to Proposition 5.18 in [BL].
Proof by authority My good colleague Andrew said he thought he might have come up with a proof of this a few years ago...
Internet reference For those interested, the result is shown on the web page of this book. Which unfortunately doesn't exist any more.
Proof by avoidanceChapter 3: The proof of this is delayed until Chapter 7 when we have developed the theory even further. Chapter 7: To make things easy, we only prove it for the case , but the general case in handled in Appendix C. Appendix C: The formal proof is beyond the scope of this book, but of course, our intuition knows this to be true.
这是因为 —— 想到这个问题的答案并不容易 —— 地球是圆的。下图就是人站在地球上看日出的一个比例夸张版示意图，其中 O 为地球的中心，A 为人眼的位置，AB 为视平线，B 点为水天交界处。由于太阳距离我们相当遥远，因此我们把太阳光看作是一束理想的平行光线。我们把直接射入人眼的太阳光与 AB 的夹角记为，把经过水面上的一点 C 反射进入人眼的光线与 AB 的夹角记为。从图上可见，视角比小，也就是说太阳在水面上的镜像比本身要小一些。