分析思考二次函数在闭(或半闭半开)区间上的问题,一是要弄清抛物线的对称轴与区间的位置关系,二是要观察明了区间端点及抛物线顶点的函数值点与x轴的位置关系.这样就能找准问题的关键,把图形语言转化为数式语言,又快又准地解决问题.【例1】已知函数f(x) =x2+2xtanθ-1,x∈[-1,3 Analyze and think about the problem of the quadratic function in the closed (or semi-closed and semi-open) interval. One is to understand the positional relationship between the symmetry axis of the parabola and the interval, and the other is to observe the function value point and the interval between the endpoint of the interval and the vertices of the parabola. Axis position relationship. This will be able to identify the key to the problem, the graphics language into a digital language, quickly and accurately solve the problem. [Example 1] known function f (x) = x2 + 2xtan θ-1, x ∈ [-1,3