∠ACB = 180-60 = 120°
по теореме косинусов
AB² = AC² + BC² - 2*AC*BC*cos(∠ACB)
AB² = 4² + 3² - 2*4*3*cos(120°)
AB² = 16 + 9 - 2*12*(-1/2)
AB² = 25 + 12
AB² = 37
AB = √37
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p(3;-4)
q(15;8)
p·q = 3*15 + (-4)*8 = 45 - 32 = 17
|p| = √(3² + (-4)²) = √(9 + 16) = √25 = 5