yes
Yes
Because all other polygons are made from triangles as for example an 8 sided octagon has 6 triangles within it or a 6 sided hexagon has 4 triangles within it.
All four-sided figures are quadrilaterals.
No. There are some figures that don't have a name that are five sided.
yes
Yes
Yes
Because there are 540 interior degrees in a five sided figure and the total sum of three triangles is 540 degrees
Yes because 3*180 are the interior degrees of a pentagon.
Yes because there are 540 degrees in a pentagon and 180 degrees in a triangle so 540/180 = 3 triangles.
You can always find opposite corners that can be connected with a line which divides the quadrilateral into two trilaterals.
Because all other polygons are made from triangles as for example an 8 sided octagon has 6 triangles within it or a 6 sided hexagon has 4 triangles within it.
Yes
Yes. Take any quadrilateral, and connect 2 opposite corners with a line segment. Now you have 2 triangles.
All four-sided figures are quadrilaterals.
TRUE for 2-dimensional figure. False for 3-dimensional figures.