 One of the greatest mathematicians and astronomers in the 14th century India, Madhava, linked the idea of infinite series with geometry and trigonometry. He was able to formulate infinite series expansions for sine, cosine, arctan, and even pi. So you see these expansions here? You know the one that we call the power series expansions, but nope, they're actually called the Madhava series. This is the Madhava sine series, this is the Madhava cosine series, and this is the Madhava arctangent series. But if he did find this, then why didn't Madhava get the credit himself? We can't find his work. The only sources were the mathematicians who referenced him. Newton and Libnitz and other Western mathematicians were 300 years too late.