src/HOL/Complex/ex/ASeries_Complex.thy
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     1 (*  Title:      HOL/Library/ASeries.thy
       
     2     ID:         $Id$
       
     3     Author:     Benjamin Porter, 2006
       
     4 *)
       
     5 
       
     6 
       
     7 header {* Arithmetic Series for Reals *}
       
     8 
       
     9 theory ASeries_Complex
       
    10 imports Complex_Main ASeries
       
    11 begin
       
    12 
       
    13 lemma arith_series_real:
       
    14   "(2::real) * (\<Sum>i\<in>{..<n}. a + of_nat i * d) =
       
    15   of_nat n * (a + (a + of_nat(n - 1)*d))"
       
    16 proof -
       
    17   have
       
    18     "((1::real) + 1) * (\<Sum>i\<in>{..<n}. a + of_nat(i)*d) =
       
    19     of_nat(n) * (a + (a + of_nat(n - 1)*d))"
       
    20     by (rule arith_series_general)
       
    21   thus ?thesis by simp
       
    22 qed
       
    23 
       
    24 end