Bhāskarāchārya / Bhāskara II (1114–1185) was an Indian mathematician and astronomer.
Among his many achievements are the following:
1. He was the first person to explain that when you divide by zero, the result is infinity.
2. He was also the first person to note that a positive number has two square roots - a positive and a negative one.
3. He described the principles of differential calculus 500 years before Leibniz and Newton. (He definitively came up with Rolle’s theorem half a millennium before Rolle himself.)
4. He calculated the length of the rotation of the earth around the sun to 365.2588 days - he was just off by 3 minutes.
Intriguingly, his treatise on arithmetic and geometry, Līlāvatī, is named after his daughter. He addresses her as an eager student:
Oh Līlāvatī, intelligent girl, if you understand addition and subtraction, tell me the sum of the amounts 2, 5, 32, 193, 18, 10, and 100, as well as [the remainder of] those when subtracted from 10000.” and “Fawn-eyed child Līlāvatī, tell me, how much is the number [resulting from] 135 multiplied by 12, if you understand multiplication by separate parts and by separate digits. And tell [me], beautiful one, how much is that product divided by the same multiplier?
These invocations have led some to surmise that Līlāvatī, too, was a mathematician.
Image from here: http://mathdept.ucr.edu/pdf/iwm1.pdf
Story of her introduction to math here: http://4go10tales.blogspot.co.uk/2012/06/lilavati.html
Wikipedia on Bhaskaracharya