What is the total surface area of pyramid FBGE ?

請列式 , Thanks ...

area of ΔEFB (same as EFG & FGB) = √(2 X 20^2) (pyth. theorem) = √2 X 20
area of ΔEGB = 1/2 X (√2 X 20) X (√2 X 20 X sin60°) = √3 X 200

area of FBGE = (√2 X 20) X 3 + √3 X 200

gzbus :area of ΔEFB (same as EFG & FGB) = √(2 X 20^2) (pyth. theorem) = √2 X 20
area of ΔEGB = 1/2 X (√2 X 20) X (√2 X 20 X sin60°) = √3 X 200

area of FBGE = (√2 X 20) X 3 + √3 X 200

點解無啦啦 sin60°既 ?

假設 EB 系個 eq.Δ o既底邊.
o甘個高就是 G同佢 垂直project落 EB o既點 (例如叫K)
area of ΔEGB = 1/2 X EB X GK
而 EG 就系條斜邊, GK = EG sinθ
θ = 60° ( 因為ΔEGB 系 eq.Δ )

PS sin60° = √3/2