tg(∠A) = BC/AC = 3,
AC = BC/3 = 18/3 = 6,
По теореме Пифагора:
AB² = AC² + BC² = 6² + 18² = 6² + 6²·3² = 6²·(1 + 3²),
AB² = 6²·10,
AB = √(6²·10) = 6·(√10)
tg(∠A) = BC/AC = 3,
AC = BC/3 = 18/3 = 6,
По теореме Пифагора:
AB² = AC² + BC² = 6² + 18² = 6² + 6²·3² = 6²·(1 + 3²),
AB² = 6²·10,
AB = √(6²·10) = 6·(√10)