A sector of a circle with radius 5cm and an angle of π/3 subtended at the centre is a cardboard. It is then curved around to form a cone. Find its exact surface area and volume.
answer: 25π/6 cm^2
where is the radius and the slant-height of the cone.
So if the radius of the original cardboard circle is cm, can you see that this means that when the cardboard is formed into a cone?
So you can now:
- Use the formula above to find , given that
- Use Pythagoras' Theorem to find , the vertical height of the cone.
- Use the formula to find the volume of the cone.
Can you complete it now?