objective: to be able to use the formula for the curved surface area of a cone, alongside other...
TRANSCRIPT
Objective: To be able to use the formula for the Curved Surface Area of a Cone, alongside other mathematical topics
Starter
Calculate the Area and Perimeter of this sector of a circle
6cm
220°
Area of the sector: Perimeter of the sector:
(Add on the 2 radii)
Curved Surface Area of a Cone
• Today we will see how to find the Surface Area of a Cone
• The base of a Cone is a circle which we have already seen how to work out
• The new part is the Curved Surface Area around the top…
Base
Curved Surface Area
Curved Surface Area of a Cone
r
l
l
θ
Area of the sector:
Base Circumference = 2πr
2πr
Circumference of the sector:The circumference of the base of the cone is equal to the arc length on the sector…
(This sector is made by unfolding the curved area
of the cone)
C = 2πr
Divide by 2π
Multiply by 360
Divide by l
Swap the ÷ 360
Replace θ from the previous
equation
Top x Top Bottom x Bottom
Cancel the 360s and an l from top and
bottom
Curved Surface Area of a Cone
Curved Surface Area of a Cone = πrlr = the radius of the base of the
Cone
l = the length of the slope of the
cone
r
l
Objective: To be able to use the formula for the Curved Surface Area of a Cone, alongside other mathematical topics
Curved Surface Area of a Cone
• Calculate the Surface Area of this Cone
4cm
10cm
Objective: To be able to use the formula for the Curved Surface Area of a Cone, alongside other mathematical topics
Curved Surface Area of a Cone
• Calculate the Curved Surface Area of this Cone
3cm
6cm
You will need to use Pythagoras’ Theorem to find the slant height…
Objective: To be able to use the formula for the Curved Surface Area of a Cone, alongside other mathematical topics
PlenaryCurved SA of the Cone
Curved SA of the Cylinder
The Base
In Total
Objective: To be able to use the formula for the Curved Surface Area of a Cone, alongside other mathematical topics
Plenary
Summary
• We have learnt how to work out the Surface Area of a Cone
• We have seen where the formula comes from
• We have used it alongside other topics we have covered