Prisma ABCD . EFGH dengan alas berbentuk layang - layang . Keliling ABCD 108 cm , AB=20cm , BD=32cm , AE=8cm. Tentukan luas permukaan prisma & volume .
EdhyR
Diketahui : ABCD = 108 cm = Ka AB = AD = 20 cm = s1 BC = DC = ...? = s2 BD = 32 cm = d1 AC = ...? = d2 AE = 8 cm = t prisma O = titik pusat layang-layang
BC = 1/2 ( ABCD - 2 x AB ) = 1/2 ( 108 - 2 x 20 ) = 1/2 ( 108 - 40 ) = 1/2 x 68 = 34 cm AO = √AD² - OD² = √20² - 16² = √400 - 256 = √144 = 12 cm OC = √BC² - BO² = √34² - 16² = √1156 - 256 = √900 = 30 cm AC = AO + OC = 12 + 30 = 42 cm LP = 2 La + ABCD x AE = 2 ( 1/2 x BD x AC ) + 108 x 8 = 2 ( 1/2 x 32 x 42 ) + 864 = 2 ( 16 x 42 ) + 864 = 2 x 672 + 864 = 1344 + 864 = 2208 cm² V = La x AE = 672 x 8 = 5376 cm³
ABCD = 108 cm = Ka
AB = AD = 20 cm = s1
BC = DC = ...? = s2
BD = 32 cm = d1
AC = ...? = d2
AE = 8 cm = t prisma
O = titik pusat layang-layang
BC = 1/2 ( ABCD - 2 x AB )
= 1/2 ( 108 - 2 x 20 )
= 1/2 ( 108 - 40 )
= 1/2 x 68
= 34 cm
AO = √AD² - OD²
= √20² - 16²
= √400 - 256
= √144 = 12 cm
OC = √BC² - BO²
= √34² - 16²
= √1156 - 256
= √900 = 30 cm
AC = AO + OC
= 12 + 30
= 42 cm
LP = 2 La + ABCD x AE
= 2 ( 1/2 x BD x AC ) + 108 x 8
= 2 ( 1/2 x 32 x 42 ) + 864
= 2 ( 16 x 42 ) + 864
= 2 x 672 + 864
= 1344 + 864
= 2208 cm²
V = La x AE
= 672 x 8
= 5376 cm³