Lagrange Mean Value Theorem 3D Visualization
如果函数 f(x) 满足：
1. 在闭区间 [a,b] 上连续
2. 在开区间 (a,b) 内可导
那么至少存在一点 ξ ∈ (a,b)，使得：
f'(ξ) = [f(b)-f(a)]/(b-a)
If function f(x) satisfies:
1. Continuous on closed interval [a,b]
2. Differentiable on open interval (a,b)
Then there exists at least one point ξ ∈ (a,b) such that:
f'(ξ) = [f(b)-f(a)]/(b-a)
连接曲线两端点的割线斜率等于曲线上某点的切线斜率
The slope of the secant line connecting the endpoints equals the slope of the tangent line at some point on the curve