I will rephrase your question as "What shape has only three right angles?" A shape is a 2D drawing that encloses some space. The sum of the angles must exceed 270 degrees. A rectangle is out of the question as it has four right angles. But a 5 sided shape with unequal sides (irregular pentagon) or higher number of sides is fine. I wish Wikipedia would let draw on these answers, because I could draw hundreds of shapes with three right angles. When we talk of shapes, the most regular shapes come to mind, triangles, squares, pentagons, etc. But you did not spcify that my shape had to have straight sides. Imagine, for example, a circle which I will break at three places and insert right angles. Weird, but it does have three right angles. Do the right angles have to face in towards the center? I could even draw a more bizarre shape with with three right angles facing out, connected by curved lines.
A Triangle drawn accross a sphere; NOT on a plane surface.
a Pentagon is five sided and CAN have 3 right angles.
you cannot make a regular shape which has 3 right angles only, you will always end up with 4 right angles
An irregular hexagon.
a decagon
No shape does: if it has three angles the sum of the angles will be 180°, but 2 right angles is 2 x 90° = 180° which means the third angle cannot exist.
Yes it can. Imagine a square with the corner cut off. The remaining shape is a pentagon with three right angles.
It doesn't have to, but it can. A trapezoid is any shape in which there is a pair of parallel sides. This means that a square can be classified as a trapezoid. But notice that a four-sided shape can never have ONLY three 90° angles. The sum of angles of a four-sided shape is 360--this means that if you have three 90° angles, then the remaining angle must be 360-3(90) which is 90°, giving you four right angles. * * * * * No you cannot. As indicated in the second paragraph of the above answer, three right angles implies that all four angles are right angles and that makes the figure a rectangle (or a square).
A right angled triangle.
An irregular hexagon.
its impossible; the two perpendicular lines already make four right angles.
That's three different shapes: a rectangle, a rhombus and a trapezoid respectively.