First, find the area of the base. This base can be any polygon, but for the example, I am going to be using a square for the base. Multiply the length of the base times the width of the base.
Next, find the area of the lateral faces. These lateral faces are simply the triangles on the side that lead up to the point of the pyramid. You can do this by doing base times height of the triangle, then divide it by 2. You have to do this separately for shapes with different lengths for different sides of the bases, but with a square, you can multiply this number by 4, since there are 4 equal sides to a square.
l × w = base
b × h ÷ 2 = lateral face
I am not a professional, simply using prior knowledge!
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