直线的斜率 k 是倾斜角θ(∈[0,π))的函数:k=tgθ,θ∈[0,π/2)∪(π/2,π).其图象如下(图中实线部分):我们不妨称之为“斜率曲线”它是正切曲线的一部分,不难看出 k 分别在区间[0,π/2)、(π/2,π)上单调递增,充分考察“斜率曲线”的特征性质,可开拓解题思路,寻得解题简 The slope of the line k is a function of the tilt angle θ (∈[0,π)): k=tgθ,θ∈[0,π/2)∪(π/2,π). The image is as follows (solid line in the figure Part): We may call it a “slope curve.” It is part of the tangent curve. It is not difficult to see that k is monotonically increasing in the interval [0, π/2), (π/2, π), and the “slope curve” is fully examined. The nature of the feature can open up the problem-solving ideas and find a solution to the problem.