LINGKARAN

1.

K = 2πr

= 2 × 3,14 × 10

= 62,8 cm

2.

L = πr²

3,14 × r² = 1.256

r² = 400

r = 20 cm

3.

K = 2πr = 2 × 22/7 × 35

= 220 cm

Jarak = 220 cm × 5 kali = 1.100 cm = 11 meter

Jarak = 220 cm × 12 kali = 2.640 cm = 264 dm

Jarak = 220 cm × 42 kali = 9.240 cm = 924 dm

4.

<BOC + <AOB = 180°

72° + <AOB = 180°

<AOB = 108°

maka L Juring AOB = πr² × 108/360

= πr² × 59/180

L.BOC = πr² × sudut/360

45 = πr² × 72/360

45 = πr² × 36/180

45 × 3 = πr² × 36/180 × 3

135 cm² = πr² × 108/360 = L Juring AOB

5.

busur AC = 2πr × sudut/360

= 2 × 3,14 × 25 × 120/360

= 157/3

= 52,33 cm

L Juring AOC = πr² × sudut/360

= 3,14 × 25² × 120/360

= 654,16 cm²

L segitiga AOC = ½r² sin (sudut)

= ½ × 25² × sin 120°

= 625/2 × ½√3

= 156,25√3 cm²

≈ 270,63 cm²

L tembereng = L Juring - L segitiga

= 654,16 -270,63

= 383,53 cm²