isabelle/valid/amc12b_2003_p6.thy (14 lines of code) (raw):
(*
Authors: Wenda Li
*)
theory amc12b_2003_p6 imports
Complex_Main
begin
theorem amc12b_2003_p6:
fixes a r::real and u::"nat \<Rightarrow> real"
assumes "\<forall> k. u k = a * r^k"
and "u 1= 2"
and "u 3=6"
shows "u 0 = 2/ sqrt 3 \<or> u 0 = - 2/sqrt 3"
sorry
end