Why Does Math Work ... If It's Not Real?

According to G. H. Hardy, the 'real' mathematics of the greats like Fermat and Euler is 'useless, ' and thus the work of mathematicians should not be judged on its applicability to real-world problems. Yet, mysteriously, much of mathematics used in modern science and technology was derived from this 'useless' mathematics. Mobile phone technology is based on trig functions, which were invented centuries ago.