pizza, pyramid, mountains, beak of particular birds, etc
If you asking where you'd find them in the real world - Binoculars and telescopes are two examples.
There is no such thing as a "triangular" number (as a number), a triangular number or triangle number counts the objects that can form an equilateral triangle. One object can and Three objects can but not Two objects.
prism
A triangular number or triangle number counts the objects that can form an equilateral triangle. 10 objects can be formed into an equilateral triangle.
a basketball, a gumball, or a bowl
roof
Some of the pyramids in Antarctica resemble a triangular pyramid.
Roof of a house
tent
If you asking where you'd find them in the real world - Binoculars and telescopes are two examples.
what is the study of the design, form and function of objects in the real world
There is no such thing as a "triangular" number (as a number), a triangular number or triangle number counts the objects that can form an equilateral triangle. One object can and Three objects can but not Two objects.
Tent.
prism
Toblarone
a tent
nothing