AlKHAYYAM c.1044  c.1123 Arab Mathematician 

Omar AlKhayyam, an astronomer, mathematician, and philosopher from Persia,
worked at the court of the turkish Seljuk Sultan.
Based on his astronomical observations AlKhayyam created the most exact calendar up to that time. He developed a method for the solution of equations based on geometry and he made major contributions in Mathematics, particularly in Algebra. In the West, he is best known for his poetic work 'Rubaiyat' which was translated by Edward Fitzgerald in 1859. His themes involved complex mystical and philosophical thoughts. Although a pious Muslim, in his later life he developed a freethinking philosophy. 
www link : Biography
From the University of St. Andrews, Scotland  School of Mathematics 