What are twenty or more geometrical facts about triangles?

Answer 1

1 They are 2 dimensional 3 sided shapes

2 They are in the class of polygons known as triangles

3 They have 3 interior angles adding to 180 degrees

4 They have 3 exterior angles adding to 360 degrees

5 They can be scalene having 3 acute angles

6 They can be obtuse having 1 obtuse angle and 2 acute angles

7 They can be right having a 90 degree angle and 2 acute angles

8 They can be isosceles having 2 equal angles and another angle

9 They can be equilateral having 3 equal angles of 60 degrees

10 They have no diagonals

11 They will tessellate

12 They have lines of symmetry when as equilateral or isosceles triangles

13 They have a perimeter which is the sum of their 3 sides

14 They have an area which is 0.5*base*altitude

15 Theyalso cantheir area calculated as 0.5*a*b*sinC

16 They can be doubled up into quadrilaterals

17 They can claim that all polygons are made from them

18 They are subjected to trigonometry meaning 3 measurements

19 They can be subjected to Pythagoras' theorem: a2+b2 = c2 asright triangles

20 They are subjected to the Sine Rule: a/sinA = b/sinB = c/sinA

21 They are subjected to the Cosine Rule: a2 = b2+c2-2bc*cosA

22 They are very friendly with the pyramids

23 Note that a, b and c are the sides whereas A, B and C are their opposite angles