A shape with three sides is called a triangle: 3 equal sides = equilateral 2 sides same length = isosceles 1 right angle = right-angled triangle
A right angle triangle
A trapezoid can have 4 equal sides and one right angle.
No shape does. If it has 4 sides and one pair of parallel lines it cannot have only 1 right angle, it must either have: 1) 2 right angles, 1 acute acute and 1 obtuse angle; or 2) no right angles, 2 acute angles and 2 obtuse angles; in which case it would be a trapezium (trapezoid).
A square
Well, honey, that's a right triangle. It's like a regular triangle, but with a sassy little right angle thrown in there to keep things interesting. So, if you're looking for a shape that's all about that right angle life, you've found it.
A right-angle triangle.
A Triangle~!
A right angled triangle.
A square or a rectangle.
a ploygon or quadrilateral
no
A rhombus.
a trapezoid
triangle
an "irregular pentagon"
trapezoid