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₪ Diketahui
1. BD = 24 cm, AB = 13 cm, K = 66 cm
2. d1 = 12 cm, K = 40 cm
? Ditanya
1. AC
2. Luas Belah Ketupat
✏ Penyelesaian
1. Panjang AO
AO² = AB² – BO²
AO² = AB² – ( BD ÷ 2 )²
AO² = 13² – ( 24 ÷ 2 )²
AO² = 13² – 12²
AO² = 169 – 144
AO² = 25
AO = √25
AO = 5 cm
Panjang CD ( sama dengan BC )
K = AB + AD + CD + BC
66 = 13 + 13 + 2CD
66 = 26 + 2CD
2CD = 40
CD = 20 cm
Panjang CO
CO² = CD² – DO²
CO² = 20² – ( BD ÷ 2 )²
CO² = 20² – ( 24 ÷ 2 )²
CO² = 20² – 12²
CO² = 400 – 144
CO² = 256
CO = √256
CO = 16 cm
Panjang AC
= AO + CO
= 5 cm + 16 cm
= 21 cm
2. K = 4s
40 = 4s
s = 10 cm
Panjang Diagonal
a² = b² – c²
a² = 10² – ( 12 ÷ 2 )²
a² = 100 – 36
a = √64
a = 8 cm
d2 = 2a
= 2 × 8
= 16 cm
Luas Belah Ketupat
= ½ × d1 × d2
= ½ × 12 × 16
= 6 × 16
= 96 cm²