Add more math courses.

docs/courses/mit/course-18.md

@@ -14,14 +14,15 @@ Fall/Spring classes:
 - ✅ 18.01 [Calculus](/courses/mit/course-18/18-01/) (Fall 2006 - Fall 2010)
 - ✅ 18.02 [Multivariable Calculus](/courses/mit/course-18/18-02/) (Fall 2007 - Fall 2021)
 - ✅ 18.03 [Differential Equations](/courses/mit/course-18/18-03/) (Spring 2006 - Spring 2020)
+- ✅ 18.04 [Complex Variables with Applications](/courses/mit/course-18/18-04/) (Fall 2023)
 - ✅ 18.05: [Introduction to Probability and Statistics](/courses/mit/course-18/18-05/) (Fall 2022)
 - ✅ 18.06: [Linear Algebra](https://web.mit.edu/18.06/www/) (Fall 2004 - Fall 2023)
 - 🔄 18.700 [Linear Algebra](/courses/mit/course-18/18-700/) (Fall 2022), <span style="color:red">no solutions/exams</span>
 - 🔄 18.701 [Algebra I](/courses/mit/course-18/18-701/) (Fall 2021), <span style="color:red">no exams</span>
 - 🔄 18.702 [Algebra II](/courses/mit/course-18/18-702/) (Spring 2022), <span style="color:red">no solutions</span>
 - ✅ 18.100A/B [Real Analysis](/courses/mit/course-18/18-100/) (Fall 2002 - Fall 2024)
-
 - ✅ 18.901 [Introduction to Topology](https://math.mit.edu/~jhirsh/topology.html) (Spring 2016)
+
 - ✅ 18.783: [Elliptic Curves](https://math.mit.edu/classes/18.783/2023/) (Fall 2023)
 - 🔄 18.405 [Advanced Complexity Theory](/courses/mit/course-18/18-405/) (Spring 2024), <span style="color:red">no solutions</span>
 - 🔄 18.435 [Quantum Computation](/courses/mit/course-18/18-435/) (Fall 2023), <span style="color:red">no recent homeworks/exams</span>

docs/courses/mit/course-18/18-03.md

@@ -14,6 +14,7 @@ Also see the math department's [subject overview](https://math.mit.edu/academics
 - Spring 2020 [class website](https://math.mit.edu/~dyatlov/18.03/#lectures) (homework, solutions, recitations)
 - Spring 2018 [lecture notes](https://math.mit.edu/~poonen/notes03.pdf)
   - In recent years the 18.03 curriculum has been modernized, in particular to incorporate more linear algebra.
+- Fall 2018 [lecture notes](https://math.mit.edu/~dunkel/Teach/18.03/2018_CourseNotes.pdf)
 - Fall 2011 [OCW](https://ocw.mit.edu/courses/18-03sc-differential-equations-fall-2011/) (homework, solutions, exams, [lecture videos](https://www.youtube.com/watch?v=76WdBlGpxVw&list=PL64BDFBDA2AF24F7E))
 - Fall 2010 [OCW](https://ocw.mit.edu/courses/18-03sc-differential-equations-fall-2011/) (homework, solutions, exams)
 - Fall 2009 (18.034) [OCW](https://ocw.mit.edu/courses/18-034-honors-differential-equations-spring-2009/) (homework, solutions, lecture notes)

docs/courses/mit/course-18/18-04.md

@@ -0,0 +1,16 @@
+---
+layout: page
+title: 18.04 Complex Variables with Applications
+permalink: /courses/mit/course-18/18-04/
+---
+
+**Catalog description:**
+\\
+Complex algebra and functions; analyticity; contour integration, Cauchy's theorem; singularities, Taylor and Laurent series; residues, evaluation of integrals; multivalued functions, potential theory in two dimensions; Fourier analysis, Laplace transforms, and partial differential equations.
+
+Also see the math department's [subject overview](https://math.mit.edu/academics/undergrad/subjects/180x.html) for introductory math courses.
+
+### Resources:
+- Fall 2023 [class website](https://math.mit.edu/classes/18.04/2023fa/index.html) (some homework, some solutions)
+- Spring 2019 [lecture notes](https://math.mit.edu/~dunkel/Teach/18.04_2019S/notes/1804_Main.pdf)
+- Spring 2018 [OCW](https://ocw.mit.edu/courses/18-04-complex-variables-with-applications-spring-2018/) (homework, solutions, exams, lecture notes, recitation notes)

docs/courses/mit/course-18/18-05.md

@@ -6,7 +6,7 @@ permalink: /courses/mit/course-18/18-05/
 
 **Catalog description:**
 \\
-Study of differential equations, including modeling physical systems. Solution of first-order ODEs by analytical, graphical, and numerical methods. Linear ODEs with constant coefficients. Complex numbers and exponentials. Inhomogeneous equations: polynomial, sinusoidal, and exponential inputs. Oscillations, damping, resonance. Fourier series. Matrices, eigenvalues, eigenvectors, diagonalization. First order linear systems: normal modes, matrix exponentials, variation of parameters. Heat equation, wave equation. Nonlinear autonomous systems: critical point analysis, phase plane diagrams.
+Elementary introduction with applications. Basic probability models. Combinatorics. Random variables. Discrete and continuous probability distributions. Statistical estimation and testing. Confidence intervals. Introduction to linear regression.
 
 Also see the math department's [subject overview](https://math.mit.edu/academics/undergrad/subjects/180x.html) for introductory math courses.