In triangle ABC, angle B is 90, BC = 7, BA = 7√3. Find the diameter of the circumscribed circle of this triangle.

By the condition of the given problem, it follows that the triangle ABC is right-angled. Therefore, the theorem about a right-angled triangle and a circle circumscribed around it, the diameter of a circle is equal to the hypotenuse of a right-angled triangle. We know two legs BC = 7 and BA = 7√3, therefore, substituting legs in the Pythagorean theorem, we can find the hypotenuse AC. AC2 = 72 + (7√3) 2 = 49 + 49 * 3 = 196 AC = 14. Therefore, in the theorem, the hypotenuse is equal to the diameter and is equal to 14.
Answer: The diameter of the circumscribed circle is 14.