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Consider a regular pyramid with an edge length s and a slant height l.
The surface area SA of a regular pyramid can be calculated using the following formula.
SA= 1/2pl + B
In this formula, p is the perimeter of the base, B is the base area, and l is the slant height. In the case that the pyramid is not regular, the area of each lateral face has to be calculated one by one and then added to the area of the base.
As can be seen, the area of each lateral face is 12sl. Therefore, the total lateral area will be 6 times 12sl, because there are 6 congruent lateral faces. Lateral Area [0.8em] 6( 1/2sl ) = 1/2 ( 6s)l Notice that 6s is the perimeter of the base, which can be denoted by p. Then, the lateral area can be expressed as follows. Lateral Area= 1/2 pl Therefore, the formula for the surface area is obtained.
ccccc Surface Area & = & Lateral Area & + & Base [0.8em] SA & =& 1/2pl & + & B