Isosceles triangle and an equilateral triangle
A three sided closed plane figure (shape) is a triangle.
A flat three sided figure is a triangle.
A polygon refers to a plane figure that has at least three straight sides and angles. An 18 sided shape is called an octadecagon or octakaidecagon.
Isn't that an Isoceles Triangle?
Isosceles Triangle.
A three-sided figure where all three sides are the same size.
Diagonals connect corners of a figure. If you try to connect two corners of a three sided figure, the lines you draw will exactly mimic the sides of the figure. Because of this, a three sided figure has no diagonals.
Polygon is a two dimensional figure that has three or more sides. Polygons are classified by their number of sides. Three sided is a triangle. A four sided figure is a quadrilateral. A five sided figure is a pentagon and so forth. The number of angles it has is equal to the number of sides.A polygon usaally has 5sides
A four sided figure with at least one pair of parallel sides.
An isosceles triangle.
A scalene triangle
A three-dimensional trapezium is called a trapezoid. It is a four-sided figure with at least one pair of parallel sides.