Penjelasan dengan langkah-langkah:

13) Layang² ABCD

AC = 28 cm

OC = 20 cm

→ AO = 28 – 20 = 8 cm

BC = 25 cm

• OB = √(BC² – OC²)

OB = √(25² – 20²)

OB = √(625–400)

OB = √225

OB = 15 cm

• BD = 2 × OB

BD = 2 × 15

BD = 30 cm

• AB = √(AO² + OB²)

AB = √(8² + 15²)

AB = √(64 + 225)

AB = √289

AB = 17 cm

Jawaban soal

a) Luas Layang² ABCD = ½ × AC × BD

= 28 × 30

2

= 840

2

= 420 cm²

b) Keliling Layang² ABCD = 2 × (AB + BC)

= 2 × (17 + 25)

= 2 × 42

= 84 cm

14) Trapesium siku² ABCD

AB = 20 cm

CD = 15 cm

BC = 13 cm

• AD = √(BC² – [AB – CD]²)

AD = √(13² – [20 – 15]²)

AD = √(169 – 25)

AD = √144

AD = 12 cm

Jawaban soal :

a) Luas = ½ × (AB + CD) × AD

= (20 + 15) × 12

2

= 35 × 12

2

= 35 × 6

= 210 cm²

b) Keliling = AB + BC + CD + AD

= 20 + 13 + 15 + 12

= 33 + 27

= 60 cm

15) Trapesium sama kaki

sisi sejajar atas = a

sisi sejajar bawah = b

jarak antara sisi sejajar = t

sisi miring = s

a = 20 cm

b = 36 cm

c = b – a

2

c = 36 – 20

2

c = 16

2

c = 8 cm

t = 15 cm

s = √(c² + t²)

s = √(8² + 15²)

s = √(64 + 225)

s = √289

s = 17 cm

Jawaban Soal :

a) Luas = a + b × t

2

= 20 + 36 × 15

2

= 56 × 15

2

= 28 × 15

= 420 cm²

b) Keliling = a + b + 2 × s

= 20 + 36 + 2 × 17

= 56 + 34

= 90 cm