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MATH Junior High School

Answer :
20||

AB = √[BD . DC]
AB = √[2 . 10]
AB = √20
AB = √[4.5]
AB = 2√5 cm

22||

Look the Pict !
< ABC = 90°
< BCA = < BAC = 45°

AB = BC = 5 cm
AC = √[5² + 5²] = 5√2 cm

The perimeter is ...
= AB + BC + AC
= 5 + 5 + 5√2
= 10 + 5√2
= 5(2 + √2) cm

23||

Cos 60° = AB/BC
1/2 = b/12
2b = 12
b = 12/2
b = 6

Use Pythagoras...
AC = √[BC² - AB²]
AC = √[12² - 6²]
AC = √[144 - 36]
AC = √108
AC = √[36.3]
AC = 6√3 cm

20.)
bd = x = 2
ab = 2x = 2(2) = 4

21.)
2x + 40 + x + 20 = 180
3x + 60 = 180
3x = 180 - 60
3x = 120
x = 120 / 3 = 40

DCB = 2x + 40
= 2(40) + 40
= 80 + 40 = 120derajat

22.)

sisi miring untuk 90 , 45 , 45 = s√2
AC = 5√2

keliling = AB + BC + AC
keliling = 5 + 5 + 5√2
keliling = 10 + 5√2

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