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Augustus De Morgan (1806-1871)

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     Augustus De Morgan, often known as a mathematician, English algebraist, and logician, was born in southern India in June 1806.  His father, a colonel in the Indian army, died when De Morgan was ten years old.   
     De Morgan studied as a child in numerous private schools before entering Trinity College in 1823.  After his graduation, he continued his education by studying law at the Inns of Court.  He found that he was not interested in a legal career and was appointed to be the chair of mathematics at University College in London.

     His main accomplishments were in the field of logic, although he studied both probability and algebra.  He wrote a series of textbooks on arithmetic, algebra, trigonometry, calculus, complex numbers, probability, and logic.  He is known for the development of De Morgan’s Laws, which deal with the logic of relations.  This means that "all statements had to be analyzed into the form ‘A is (or is not) B,’ with the possible inclusion of ‘all’ and ‘some’" (Young, 1998, p. 143).  For example, the first law states that the negation of the statement "P and Q" is equivalent to the statement "not P or Q" (Smith, 1996, p. 137).  The second law states that the negation of the statement "P or Q" is equivalent to the statement "not P and not Q" (Smith, 1996, p. 137).

     He died in 1871, having created new ideas for other mathematicians to examine and ponder.           

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MacTutor - De Morgan

Activity #5:

De Morgan’s laws, stated in terms of sets, are shown below.  Use the Venn diagrams given below to demonstrate the equivalency of the indicated sets. (The notation A’ refers to the complement of A; that is, all elements not in the set A.)

 

Link to solution.


Picture reproduced from MacTutor History of Mathematics archive with permission.