src/HOL/Power.thy
changeset 55718 34618f031ba9
parent 55096 916b2ac758f4
child 55811 aa1acc25126b
equal deleted inserted replaced
55717:601ea66c5bcd 55718:34618f031ba9
   607 
   607 
   608 end
   608 end
   609 
   609 
   610 
   610 
   611 subsection {* Miscellaneous rules *}
   611 subsection {* Miscellaneous rules *}
       
   612 
       
   613 lemma self_le_power:
       
   614   fixes x::"'a::linordered_semidom" 
       
   615   shows "1 \<le> x \<Longrightarrow> 0 < n \<Longrightarrow> x \<le> x ^ n"
       
   616   by (metis gr_implies_not0 le_eq_less_or_eq less_one nat_le_linear power_increasing power_one_right)
   612 
   617 
   613 lemma power_eq_if: "p ^ m = (if m=0 then 1 else p * (p ^ (m - 1)))"
   618 lemma power_eq_if: "p ^ m = (if m=0 then 1 else p * (p ^ (m - 1)))"
   614   unfolding One_nat_def by (cases m) simp_all
   619   unfolding One_nat_def by (cases m) simp_all
   615 
   620 
   616 lemma power2_sum:
   621 lemma power2_sum: