Hafnani, S. Si, M. Si is a lecturer in the Department of Mathematics at the Faculty of Mathematics and Natural Sciences of Syiah Kuala University, Banda Aceh, Indonesia since 2005. She graduated from the Mathematics and Natural Sciences Faculty of Syiah Kuala University in 1999. Then, she completed her master's degree in 2005 at the Department of Mathematics Faculty of Mathematics and Natural Sciences at Bandung Institute of Technology, Bandung, Indonesia. At the Department of Mathematics, she belong to the group of Algebra, Analysis, and Geometry. The subjects she has taught Introduction to Calculus, Calculus, Fundamentals of Mathematics, Geometry, Analytical Geometry, Introduction to Real Analysis, Real Analysis, Introduction to Optimization, Advanced Linear Algebra, Introduction to Functional Analysis, Complex Functions, Econometrics, and Difference Equations.