luas juring 21 cm².jika jari jarinya 4 cm maka panjang busur itu ?

Penyelesaian:
Diket.:
Luas juring = 21 cm²
r = 4 cm
Ditanya:
Panjang busur = ....?
Jawab:
α/360° × πr² = Luas juring
α/360° × 3,14 × 4² = 21
α/360° × 3,14 × 16 = 21
α/360° × 50,24 = 21
α/360° = 21/50,24
α × 50,24 = 360° × 21
α × 50,24 = 7.560
α = 7.560/50,24
α = 150,48°

Panjang busur
= α/360° × 2πr
= 150,48°/360° × 2 × 3,14 × 4
= 3.780,0576°/360°
= 10,50016 cm

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