Cones – Part 1, Section 1
1. Complete the sentences below. Use the number of letters as quoted for each
Cones – Part 1, Section 2
1. Complete the sentences below. Use the number of letters as quoted for each
answer.
answer.
a. The central angle of the sector making the lateral face of a cone changes its
a. On a cone, the sector forms the lateral face and the central angle is at the
height. If the central angle is small, the cone will be very ____________ (4). If
___________ (4). The variable r represents the radius at the _________ (4) of
the central angle is large, the cone will be very _____________ (4).
the cone instead of the __________ (5) ______________ (6) which is
b. The lateral surface of a cone ___________ (4 with apostrophe or 6) be a
complete circle because then the cone would be completely
_________(4).
c.
represented by 𝑙.
b. The arc length formed by the sector will be represented by the
__________________ (13) at the base of the cone.
The lateral surface is not a type of ________ (4) as it is
curved.
2. Assume that a sector is made as the lateral face of a cone. The vocabulary on the
left is applicable to features of a sector. The vocabulary on the right is applicable to
2. Look at the sector below. Calculate its area, S and arc
length, 𝑙.
4𝑐𝑚
200𝑜
3. A sector has radius 2cm and arc length 5cm. Calculate its central angle. Hence,
calculate its area.
4. Show that when r = 2, the area of the sector S (cm) has the same numerical value
as the arc length (cm2).
features of a cone. Match the corresponding phrases for each with lines.
Radius
Central Angle
Arc Length
Sector Area
Circumference at the base
Lateral surface area
Slant Height
Angle formed about the apex
3. A cone has slant height 10cm and angle formed at the apex, 120o. Calculate its
lateral surface area and its circumference at the base.
4. A cone has slant height 5cm and circumference at the base 8π cm. Calculate the
angle formed about its apex. Hence, calculate its lateral surface area.