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12) 52cm : 4 = 13cm = panjang sisi √(13²-(24:2)²)=√(13²-12²)=√(169 -144)=√25=5cm =panjang setengah diagonal Jadi panjang diagonal lainnya = 5cm x 2 = 10cm L = 24cm x 10cm : 2 = 240cm² : 2 = 120cm² (c)
13) Panjang sisi miring = (Keliling - Alas) : 2 = (36cm - 10cm) : 2 = 26cm : 2 = 13cm Tinggi segitiga = (sisi miring)² - (setengah panjang alas)² = √(13² - (10cm : 2)²) = √(13² - 5²) = √(169 - 25) = √144 = 12cm L = alas x tinggi : 2 = 10cm x 12cm : 2 = 120cm² : 2 = 60cm² (a)
√(13²-(24:2)²)=√(13²-12²)=√(169 -144)=√25=5cm =panjang setengah diagonal
Jadi panjang diagonal lainnya = 5cm x 2 = 10cm
L = 24cm x 10cm : 2 = 240cm² : 2 = 120cm² (c)
13) Panjang sisi miring = (Keliling - Alas) : 2
= (36cm - 10cm) : 2
= 26cm : 2
= 13cm
Tinggi segitiga = (sisi miring)² - (setengah panjang alas)²
= √(13² - (10cm : 2)²)
= √(13² - 5²)
= √(169 - 25)
= √144
= 12cm
L = alas x tinggi : 2 = 10cm x 12cm : 2 = 120cm² : 2 = 60cm² (a)