微積分

從圖像上的斜率本身開始，用受限矩形工作台讓真正的極大值變得可見，再把極限與連續性的行為留在同一個目標點上，最後延伸到有號面積與累積量，讓變化率與總變化保持連在同一條視覺支線上。

This first calculus page stays on an honest graphing bench instead of splitting slope, limits, optimization, and accumulation into detached notation too early. Derivative as Slope / Local Rate of Change keeps the moving point, tangent line, secant line, and derivative graph linked so local steepness never drifts into symbols alone, Limits and Continuity / Approaching a Value keeps one-sided approach and continuity visible at a target point, Optimization / Maxima, Minima, and Constraints turns that local-slope language into one fixed-perimeter rectangle bench where the objective curve peaks at the square, and Integral as Accumulation / Area keeps the same graph-first language while the running total grows from signed area.