Question

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 `7`, its base has sides of length `6`, and its base has a corner with an angle of `(3 pi)/4`. What is the pyramid's surface area?

Answer 1

T S A = 116.8416

Explanation:

AB = BC = CD = DA = a = 6
Height OE = h = 7
OF = a/2 = 6/2 = 3
`EF = sqrt(EO^2+ OF^2) = sqrt (h^2 + (a/2)^2) = sqrt(7^2+3^2) = color(red)(7.6158)`

Area of `DCE = (1/2)*a*EF = (1/2)*6*7.6158 = color(red)(22.8474)`
Lateral surface area `= 4*Delta DCE = 4*22.8474 = color(blue)(91.3896)`

`/_C = pi - ((3pi)/4) = (pi)/4`
Area of base ABCD `= a* a * sin /_C = 6^2 sin (pi/4) = 25.452`

T S A `= Lateral surface area + Base area`
T S A `=91.3896 + 25.452 = color(purple)(116.8416)`