[RockyMcNuts]

Computer science is the study of algorithms, information systems and anything that is computable.

Mathematics is the study of formal systems, eg proofs that can be derived from axioms using algorithms, i.e. a specific type of computable system.

Therefore, mathematics is a subset of computer science.

[Retric]

Math includes the study of non computable things. Also, Math includes chaos theory which is more than just a formal system.

EX: computable numbers are a subset of all numbers. http://en.wikipedia.org/wiki/Computable_number

[RockyMcNuts]

mostly kidding. but presumably the theorems about non-computable numbers are computable and therefore you're still working with computable things?