Yang bisa tolong bantu bagaimana caranya

BC² = AB² + AC² - 2 × AB × BC × cosA
BC² = 6² + 10² - 2 × 6 × 10 × cos60°
BC² = 6² + 10² - 2 × 6 × 10 × ½
BC² = 36 + 100 - 60
BC² = 76
BC =√76
BC = 2√19 cm (A)