a) 64 cm²
b) 8.8 cm
a)
A = (b + B)×h/2
= (DC + AB)×BC/2
= (5cm + 11cm)×8cm/2
= 16cm×4cm
= 64 cm²
b)
A(ΔBCD) = BC×CD/2
= 8cm×5cm/2
= 20 cm²
A(ABD) = A(ABCD) - A(BCD)
= 64cm² - 20cm²
= 44 cm²
A(ABD) = BX×AD/2
44cm² = BX×10cm/2
88cm² = BX×10cm
BX = 88cm²/10cm
= 8.8 cm
