Quantum redactiones paginae "Numerus triangularis" differant

m
+{{imago sine descriptione}}; mutationes minores
m (+{{imago sine descriptione}}; mutationes minores)
{| border="1" align="right" cellpadding="8" style="margin-left: 1em"
|1
|[[ImagoFasciculus:Triangular number 1.png|{{imago sine descriptione}}]]
|-
|3
|[[ImagoFasciculus:Triangular number 3.png|{{imago sine descriptione}}]]
|-
|6
|[[ImagoFasciculus:Triangular number 6.png|{{imago sine descriptione}}]]
|-
|10
|[[ImagoFasciculus:Triangular number 10.png|{{imago sine descriptione}}]]
|-
|15
|[[ImagoFasciculus:Triangular number 15.png|{{imago sine descriptione}}]]
|-
|}
 
 
== Proprietates ==
Una proprietas iucunda est: 2 numeri triangulares consequentes additi [[numerus quadratus|numerum quadratum]] aequant. E.g., 1 + 3 = 4 = 2^2, 3 + 6 = 9 = 3^3, 6 + 10 = 16 = 4^2, 10 + 15 = 25 = 5^2, etc. Hoc monstretur mathematico modo:
 
{| cellpadding="8"
|16
|[[ImageFasciculus:Square number 16 as sum of two triangular numbers.svg]]
|-
|25
|[[ImageFasciculus:Square number 25 as sum of two triangular numbers.svg]]
|}
Quadrati facti duobus numeris triangularibus consequentibus aduinctis.
 
In [[base 10]], the [[digital root]] of a triangular number is always 1, 3, 6 or 9. Hence every triangular number is either divisible by three or has a remainder of 1 when divided by nine:
:6 = 3×23×2,
:10 = 9×19×1+1,
:15 = 3×53×5,
:21 = 3×73×7,
:28 = 9×39×3+1,
:...
 
-->
 
== Vide etiam ==
* [[Numerus tetrahedronalis]] - 3-D versio numeri triangularis.
* [[Numerus quadratus]]
* [[666]] - Numerus triangularis notissimus.
 
== Nexus externi ==
* [http://blip.tv/file/54480 Numeri triangulares] Pellicula PodCast a http://www.isallaboutmath.com
* [http://www.cut-the-knot.org/do_you_know/numbers.shtml#square Numeri triangulares] apud [[cut-the-knot]]
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