>>10114815All mathematical disciplines make use of and include each other, much like Chemistry, Biology, Physics etc are all the same science, just different areas of science. Like you can say Chemistry is important and Psychology is useless, but Psychologists are just sacks of chemicals trying to predict and manage the behavior of other sacks of chemicals. Apply Chemistry enough and you have Psychology, apply Arithmetic enough and you have Algebra, Calculus, Statistics, etc. All of them are important.
