圆的方程可以表达为(x - 3)² + (y-4)² = 25, 圆心M(3, 4), 半径为5设过原点O的直线的斜率为k, 方程为y = kx, kx - y = 0设的中点为C, AC = 8/2 = 4, AMC为直角三角形, MC = √(MA² - AC²) = √(...