
 Monday, April 10 
  We restate the definitions of injection, surjection, and bijection using function notation: Definition: A function (A,f,B) is an injection iff (Axy E A.(f(x) = f(y) > x = y)) An injection is also said to be ``onetoone''. 
  Definition: A function (A,f,B) is a surjection iff (Ay E B.(Ex E A.(y = f(x)))) A surjection is also said to be ``onto''. 
  Definition: A function (A,f,B) is said to be a bijection iff it is both an injection and a surjection. 
 math.boisestate.edu /~holmes/M387syllabus/node54.html (650 words) 
