Which of these can be used to show that the slope of a non-vertical line is the same anywhere along the line? \( \begin{array}{ll}\text { A) acute triangles } & \text { (C) right triangles } \\ \text { (B) obtuse triangles } & \text { (D) any triangles }\end{array} \)

You can use right triangles to demonstrate that the slope of a non-vertical line remains constant. By drawing perpendicular lines from any point on the line to the x-axis, you create right triangles. The ratio of the vertical rise to the horizontal run remains the same, illustrating that the slope does not change regardless of the triangle you form along the line. Additionally, you might be intrigued to know that the concept of slope dates back to the ancient Greeks, but it wasn't formally defined until the 17th century with the work of mathematicians like Descartes. They laid the groundwork for analytic geometry, which connects algebra and geometry, providing the tools to understand slopes mathematically!