Whats L.A when your trying to find surface area of a square-based pyramid?

Guest Apr 12, 2017

LA stands for "lateral area."

Lateral area is the surface area except for the area of the base.

The lateral area of a pyramid = (1/2) * (perimeter of base) * (height)

hectictar  Apr 12, 2017

Thanks guest 


Could you please derive that formula ?

(My question is only intended for the guest who posted the formula)   smiley

Melody  Apr 12, 2017
edited by Melody  Apr 12, 2017

I am sorry what I said is actually not good, I should have said slant height...


But here is my explanation. You can see how that it is because if you take the triangles and lay them out like this:



Since the base of each triangle is the same length,

area of one blue triange = (1/2)(1/4 * perimeter of base)(slant height)


There are 4 triangles total that area all the same size.. so,

area of all blue triangles = 4 * (1/2)(1/4 * perimeter of base)(slant height)

area of all blue triangles = (1/2)(perimeter of base)(slant height)

hectictar  Apr 12, 2017
edited by hectictar  Apr 12, 2017

"L.A" of a square-based pyramid  


We have four triangles each with base edge "b"   and a slant height, "h"


And....the lateral surface area  =


4 * (1/2) b * h   =




But.....the perimeter  = 4b




2bh  =  


(1/2) 4b * h  =


(1/2) *perimeter * slant height of each face



cool cool cool

CPhill  Apr 12, 2017

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