Cone
Go to Surface Area or Volume.
Cone Facts
Notice these interesting things:
- It has a circle at one end
- And a point at the other end
- And a curved side
- It is not a polyhedron as it has a curved surface
- The pointy end of a cone is called the apex
- The flat part is the base
An object shaped like a cone is said to be conical
A Cone is a Rotated Triangle
A cone can be made by rotating a triangle!
The triangle is a right-angled triangle, and it gets rotated around one of its two short sides.
The side it rotates around is the axis of the cone.
Right vs Oblique Cone
When the apex is aligned on the center of the base it is a Right Cone otherwise it is an Oblique Cone:
Surface Area of a Cone
The Surface Area has two parts:
- The Base Area = π × r2
- The Side Area = π × r × s
Which together makes:
Surface Area = π × r × (r + s)
Note: we can calculate s = √(r2+h2)Example: h = 7 and r = 2
Total Surface Area ≈ 12.57 + 45.74 ≈ 58.31
Volume of a Cone
Volume = 1 3 π × r2 × h
Example: h = 7 and r = 2
Play with it here. The formula also works when it "leans over" (oblique) but remember that the height is always at right angles to the base:
Volume of a Cone vs Cylinder
The volume formulas for cones and cylinders are very similar:
| The volume of a cylinder is: | π × r2 × h |
| The volume of a cone is: | 1 3 π × r2 × h |
So a cone's volume is exactly one third ( 1 3 ) of a cylinder's volume.
You should order your ice creams in cylinders, not cones, you get 3 times as much!
Like a Pyramid
A cone is also like a pyramid with an infinite number of sides, see Pyramid vs Cone.
Different Shaped Cones
Construction Cone
This is almost a cone, but the top is chopped off (called a "truncated cone").
Also it has a wider base added so it doesn't fall over!