A pyramid has a base in the shape of a rhombus and a peak directly above the base's center. The pyramid's height is 2 2, its base has sides of length 1 1, and its base has a corner with an angle of (2 pi)/3 2π3. What is the pyramid's surface area?

1 Answer
Jan 27, 2018

Total Surface Area color(brown)(T S A) color(brown)(= 4.9892)TSA=4.9892

Explanation:

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Pyramid's Total Surface Area (T S A) A_TAT =Lateral Surface Area + Rhombus Base Area (A_R)(AR)

Lateral Surface Area (L S A)= 4 * Area of Slant Triangle (A_S)

i.e. A_T = A_B + (4 * A_S)AT=AB+(4AS)

To find A_B, A_SAB,AS

Let a be the rhombus side, theta the corner angle and h the height of the pyramid.

Given : a = 1, theta = (2pi)/3, h = 2a=1,θ=2π3,h=2

color(red)(A_R) = a^2 sin theta = 1^2 sin ((2pi)/3) color(red)(= sqrt3 /2 = 0.866)AR=a2sinθ=12sin(2π3)=32=0.866

A_S = (1/2) a * sqrt(h^2 + (a/2)^2)AS=(12)ah2+(a2)2

color(red)(A_S) = (1/2)(1) * sqrt(2^2 + (1/2)^2) color(red)(= 1.0308)AS=(12)(1)22+(12)2=1.0308

color(red)(T S A) = A_T = A_R + (4 * A_S) = 0.866 + (4 * 1.0308) color(red)(= 4.9892)TSA=AT=AR+(4AS)=0.866+(41.0308)=4.9892