20 1 1 the process of the last question and the third question in Xiangyang mathematics senior high school entrance examination
Because the three points A, B and C and the parabolic equation can be solved, and P 1B is perpendicular to BC, the P 1B equation (whose slope can be obtained from BC slope) can be solved simultaneously with the parabolic equation, and the intersection coordinates P 1 can be obtained. Similarly, P2A is perpendicular to AC, and P2 coordinates can be solved simultaneously by parabolic equation.