Răspuns:
Aria ferestrei = 40cm×104cm = 4160 cm²
Aria afisului = 4160cm² - 3760cm² = 400 cm²
A(afis) = 400 cm² = l² => l = 20 cm
VO = 9 cm
P(bazei) = 72cm => AB = 72/4 = 18 cm
BO = AB√2/2 = 9√2 cm
VB = √(BO² + VA²)
= √[9² + (9√²)²]
= √(9² + 9²·2)
= √9²(1 + 2)
= √9²×3
= 9√3 cm
VP(apotema) = √(VB² - BP²)
BP = AB/2 = 9 cm
= √(9√3)² - 9²
= √9²·3 - 9²
= √9²(3 - 1)
= √9²·2
= 9√2 cm
