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lys-0071 [83]
3 years ago
15

The following picture is a square pyramid where DE=8 cm and m∠ADE=60°.

Mathematics
2 answers:
Goryan [66]3 years ago
7 0

<u>Given</u>:

The length of DE is 8 cm and the measure of ∠ADE is 60°.

We need to determine the surface area of the pyramid.

<u>Length of AD:</u>

The length of AD is given by

cos 60^{\circ}=\frac{FD}{8}

       4=FD

Length of AD = 8 cm

<u>Slant height:</u>

The slant height EF can be determined using the trigonometric ratio.

Thus, we have;

     sin \ 60^{\circ}=\frac{EF}{8}

sin \ 60^{\circ} \times 8=EF

      \frac{\sqrt{3}}{2} \times 8=EF

          4\sqrt{3}=EF

Thus, the slant height EF is 4√3

<u>Surface area of the square pyramid:</u>

The surface area of the square pyramid can be determined using the formula,

SA=Area \ of \ square + \frac{1}{2} (Perimeter \ of \ base ) (slant \ height)

Substituting the values, we have;

SA=8^2+\frac{1}{2}(8+8+8+8)(4 \sqrt{3})

SA=64+\frac{1}{2}(32)(4 \sqrt{3})

SA=64+(16)(4 \sqrt{3})

SA=64+64 \sqrt{3}

The exact form of the area of the square pyramid is 64+64 \sqrt{3}

Substituting √3 = 1.732 in the above expression, we have;

SA = 64 + 110.848

SA = 174.848

Rounding off to one decimal place, we get;

SA = 174.8

Thus, the area of the square pyramid is 174.8 cm²

Anika [276]3 years ago
6 0

Answer:

174.9 cm²

Step-by-step explanation:

AD = 2 × (8cos60)

AD = 8

Base = 8²

= 64

4 triangles = 4(½ × 8 × 8sin60)

= 64sqrt(3)

SA = 64 + 64sqrt(3)

174.8512517

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