In this talk, I will briefly discuss the importance of mathematics in signal processing in electrical engineering. From my experience in USA over the past decades, I see that the most significant change in human daily life is telecommunications, such as smart phones, where mathematics plays an important role. I will briefly introduce some of the key components of math in communications: some elementary math and some more advanced math, such as, finite fields and orthogonal designs (or compositions of quadratic forms) etc. I will finally briefly show some of our results on orthogonal designs.