Napier's Inequality (I)
Napier's inequality: If , then .[more]
Observe that in the graphic, , the slope of the secant line passing through and , is between the slopes of the tangent lines at and .[less]
Reference: R. Nelsen, "Napier's Inequality (Two Proofs)," The College Mathematics Journal, 24(2), 1993 p. 165.