It depends on what information you have about the shape.
Shapes with 12 to 20 sides are named as follows: a 12-sided shape is called a dodecagon, a 13-sided shape is a triskaidecagon, a 14-sided shape is a tetradecagon, a 15-sided shape is a pentadecagon, a 16-sided shape is a hexadecagon, a 17-sided shape is a heptadecagon, an 18-sided shape is an octadecagon, a 19-sided shape is a nonadecagon, and a 20-sided shape is an icosagon.
it is length x width of a four sided shape
A one sided shape
A=(5t2 tan(54o) )/ 4
Any of these shapes is practically circular. A 20-sided shape is an icosagon. a 50-sided shape is a pentacontagon (aka pentecontagon). A 100-sided shape is a hectogon (aka hecatontagon). A 1000-sided shape is a chiliagon.
heptadecagon is a 17 sided 2d shape
A 17-gon
heptadecadon
Shapes with 12 to 20 sides are named as follows: a 12-sided shape is called a dodecagon, a 13-sided shape is a triskaidecagon, a 14-sided shape is a tetradecagon, a 15-sided shape is a pentadecagon, a 16-sided shape is a hexadecagon, a 17-sided shape is a heptadecagon, an 18-sided shape is an octadecagon, a 19-sided shape is a nonadecagon, and a 20-sided shape is an icosagon.
Heptadecagon or a Heptakaidecagon
That sounds like either a Triangle (three sided area) or a Trapezoid (four sided area).
The interior is a two-dimensional, 7-sided area.
17
it is length x width of a four sided shape
Assuming it is regular, the total degrees of an n-sided polygon = 180(n-2) = 2700. 2700/17 = 158.23 degrees
The name for a 57 sided shape is derived by combining the name for a 50 sided shape with the name for a 7 sided shape. A 57 sided shape is called a pentacontaheptagon.
A one sided shape