Flett's theorem: Given a function differentiable on with , there is an intermediate point such that[more]
Geometric interpretation: The secant line connecting the points and is exactly the tangent line to the curve at the point .
The example used is the function on the interval .[less]
T. M. Flett, "A Mean Value Theorem," Math. Gazette, 42, 1958 pp. 38–39.