Question

Help with this question, please!! I don't understand it!

Answer 1

The lateral area is the area of the cone that curves and has the length of 13m.

To calculate the lateral area you do:

π x radius x slant height

so:

π x 4 x 13 = 52π = 163.4m² (L)

To calculate the surface area, you simply add the lateral area with the area of the circular base:

Circular base area = π x radius² so π x 4² = 16π

52π + 16π = 68π = 213.6m² (S)

So the answer is:

L = 163.4m²; S = 213.6m²

Answer 2

Answer:

$\boxed{\text{L = 163.4 m}^{2};\text{ S = 213.6 m}^{2}}$

Step-by-step explanation:

Data:

d = 8 m

l = 13 m

1. Lateral surface area

The lateral surface area is the side area, excluding that of the base.

The general formula for the lateral surface area L of a cone is

L = πrl

where r represents the radius of the base and l the slant height.

The base is a circle, so

r = d/2 = 8/2 = 4 m

L =π × 4 × 13 = $\boxed{\text{163.4 m}^{2}}$

2. Total surface area

Total surface area = lateral surface area + area of base

S = L + B

The base is a circle, so

B = πr² = π(4)² = π × 16 = 50.36 m²

S = 163.4 + 50.36 = $\boxed{\text{213.6 m}^{2}}$