The problem asks to find the lateral area ($L$) and surface area ($S$) of a regular triangular pyramid, given the side length of the base ($b = 14$ ft) and the slant height ($l = 12$ ft). We need to round the answers to the nearest tenth, if necessary.

GeometrySurface AreaLateral AreaPyramidsTrianglesArea Calculation3D Geometry
2025/4/14

1. Problem Description

The problem asks to find the lateral area (LL) and surface area (SS) of a regular triangular pyramid, given the side length of the base (b=14b = 14 ft) and the slant height (l=12l = 12 ft). We need to round the answers to the nearest tenth, if necessary.

2. Solution Steps

The formula for the lateral area of a regular pyramid is:
L=12PlL = \frac{1}{2}Pl
where PP is the perimeter of the base and ll is the slant height.
The base is a triangle with side length b=14b = 14 ft. The perimeter of the triangular base is:
P=3b=3(14)=42P = 3b = 3(14) = 42 ft.
The slant height is given as l=12l = 12 ft.
Substitute these values into the lateral area formula:
L=12(42)(12)=12(504)=252L = \frac{1}{2}(42)(12) = \frac{1}{2}(504) = 252 square feet.
The formula for the surface area of a regular pyramid is:
S=L+BS = L + B
where LL is the lateral area and BB is the area of the base.
We already found L=252L = 252 square feet. Now we need to find the area of the triangular base BB. Since the problem stated "assume a base that appears to be a regular polygon is a regular polygon", we assume the base is an equilateral triangle.
The area of an equilateral triangle with side bb is:
B=34b2B = \frac{\sqrt{3}}{4}b^2
B=34(14)2=34(196)=49349(1.732)84.86884.9B = \frac{\sqrt{3}}{4}(14)^2 = \frac{\sqrt{3}}{4}(196) = 49\sqrt{3} \approx 49(1.732) \approx 84.868 \approx 84.9 square feet.
Now we can find the surface area:
S=L+B=252+493252+84.868336.868336.9S = L + B = 252 + 49\sqrt{3} \approx 252 + 84.868 \approx 336.868 \approx 336.9 square feet.

3. Final Answer

L ≈ 252.0 ft2ft^2
S ≈ 336.9 ft2ft^2

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