In this article we prove the Leibniz series for π which states that π4=∑n=0∞(−1)n2⋅n+1. $$\frac{\pi }{4}=\sum _{n=0}^{\infty }\frac{{\left(-1\right)}^n}{2·n+1}.$$ The formalization follows K. Knopp [8], [1] and [6]. Leibniz’s Series for Pi is item 26 from the “Formalizing 100 Theorems” list maintained by Freek Wiedijk at http://www.cs.ru.nl/F.Wiedijk/100/.

In this study, we obtain a local approximation theorems for a certain family of positive linear operators via I-convergence by using the first and the second modulus of continuities and the elements of Lipschitz class functions. We also give an example to show that the classical Korovkin Theory does not work but the theory works in I-convergence sense.