Hexagon
No, not if it is a randomly-drawn 8-vertex shape. Octagons only have all- obtuse angles if it is a regular octagon, like the shape of a stop sign.
Yes the interior angles of a regular octagon are obtuse.
this shape would be a rhombus
An octahedron is a closed 3-d shape with 8 polygonal faces. There are 257 topologically different convex octahedra. In addition there are concave octahedra. Some of these will have no obtuse angles, others will have several.
2 obtuse and 2 acute in the classic kite shape.
It depends on they type of arrowhead you have. If it is a arrowhead in the shape of a directional arrow, there are no obtuse angles. The most possible obtuse angles is 1.
There is no three-sided shape with two obtuse angles, because the three interior angles of a three-sided shape, which is a triangle, add up to 180 degrees, and two obtuse angles would be over 180 degrees.
supplementary angles
a pentagon
None.
None.