平面直角坐标系在实际问题中的应用非常广泛,建立不同的坐标系,抛物线的解析式就不同,但问题的答案却是相同的,只是解答时的繁简程度不同,所以选择恰当的方法建立坐标系十分必要.例如,河上有一座抛物线拱桥,拱桥下的水面离桥孔顶部3m时,水面宽为6m,当水位上升1m时,水面宽为多少?方法1:以桥孔的最高点为原点,过原点的水平线为x轴,过原点的铅垂线为y轴, Plane Cartesian coordinate system is widely used in practical problems. To establish different coordinate systems, the parabola’s analytical formula is different, but the answers to the questions are the same, but the answers to the questions are not the same, so choose the appropriate method to establish For example, the river has a parabolic arch bridge, the water under the arch bridge 3m from the top of the bridge when the water is 6m wide, when the water level rise 1m, the water surface width for how? Method 1: The highest point of the bridge as the starting point, The horizontal line through the origin is the x-axis, the vertical line through the origin is the y-axis,