Update

math.md

@@ -19,7 +19,7 @@ Following are some math areas and topics which a programmer should be familiar w
 - **formal [logic](logic.md)**: computers are based on [Boolean](boolean.md) logic, knowing basic formulas and theorems here is crucial (e.g. the completeness of [NAND](nand.md) or [De Morgan's laws](de_morgan.md)), formal logic is also just generally used in formal texts, one should know about predicate vs propositional logic etc.
 - **[proofs](proof.md)**: core of high level mathematics, one should know the basic proof techniques (direct, [contradiction](contradiction.md), [induction](induction.md), ...).
 - **[linear algebra](linear_algebra.md)**: aka "vectors and matrices", essential in almost every field ([graphics](graphics.md), [machine learning](machine_learning.md), ...).
-- **[calculus](calculus.md) and differential equations**: just essential for advanced math and many fields (graphics, machine learning, [electronics](electronics.md), physics, any optimization, ...).
+- **[calculus](calculus.md) and [differential equations](differential_equation.md)**: just essential for advanced math and many fields (graphics, machine learning, [electronics](electronics.md), physics, any optimization, ...).
 - **theoretical [computer science](compsci.md)**: [computational complexity](computational_complexity.md) (very important), [computability](computability.md), [formal languages](formal_language.md), computational models ([automata](automaton.md), [Turing machines](turing_machine.md), ...), ...
 - **[graph theory](graph.md)**: generally useful tools, especially important e.g. in networks or indexing structures in [databases](database.md).
 - **[number](number.md) and [set](set.md) theory**: sets of numbers ([natural](natural_number.md), [rational](rational_number.md), [real](real_number.md), [complex](complex_number.md), ...), [prime numbers](prime.md) (important e.g. for [cryptography](cryptography.md), [quantum computing](quantum.md), ...), ...