Coordinates of points a, b and d; Connect the CD, cross the origin O so that OE is perpendicular to the CD, the vertical foot is H, and the OE intersects the parabola symmetry axis at point E, and connect AE and AD AD. It is proved that angle AEO= angle ADC；; This problem is the finale of quadratic function, which involves many test sites and is very difficult. This is the answer/exercise/math /800480. In problem (2), pay attention to the graph, turn the problem into a problem of proving that △ADE is a right triangle, and solve it by using Pythagorean theorem and its inverse theorem and trigonometric function (or similar shape) comprehensively. In the problem (3), the key to solving the problem is to turn the maximum problem into the problem of finding the minimum value of EP2, and pay attention to the specific method of finding the minimum value of EP2 in the solution.
If you master the key points, the problem will be solved. If you think it is helpful, don't forget to adopt it ~ I wish you progress in your study and come on ~