It is a plane figure, for example, a semicircle, a triangle, a kite.
A right angle triangle will fit into a semicircle.
Diameter of semicircle = 1 Area of semicircle = Pi/8 Area of triangle = 0.25 Area outside triangle = (Pi/8) - 0.25 = 0.1427 (rounded to 4th decimal).
All triangles inscribed in a semicircle with one side of the triangle being the diameter of the semicircle are right triangles.
Figures are not solid.
A semicircle
If all the angles are equal and acute, it will be an equilateral triangle.
A semicircle?
The only rectilinear figure is a triangle, or one composed of several triangles joined together.
90
A quarter of a whole circle or half a semicircle
yes, a triangle is a closed figure