Make a circle through a (a, 0): x ^ 2 + y ^ 2 = R ^ 2 (a > R > 0), and find the path of the middle point of the chord cut by circle o

Make a circle through a (a, 0): x ^ 2 + y ^ 2 = R ^ 2 (a > R > 0), and find the path of the middle point of the chord cut by circle o

Let B (x, y) connect ob, ob ⊥ AB can be known from the vertical diameter theorem, and then OA ^ 2 + AB ^ 2 = a ^ 2 can be obtained from Pythagorean theorem, so there is x ^ 2 + y ^ 2 + (x-a) ^ 2 + y ^ 2 = a ^ 22x ^ 2 + 2Y ^ 2-2ax = 0 to form the standard formula: (x-a / 2) ^ 2 + y ^ 2 = (a ^ 2) / 4, where the value range of X is [0, R ^ 2 / a)