start vector notes

diff --git a/spec/graphics/vectors-intro.png b/spec/graphics/vectors-intro.png
new file mode 100644 (file)
index 0000000..29aa89d
Binary files /dev/null and b/spec/graphics/vectors-intro.png differ

diff --git a/spec/vectors.md b/spec/vectors.md
new file mode 100644 (file)
index 0000000..4c73237
--- /dev/null
+++ b/spec/vectors.md
@@ -0,0 +1,11 @@
+# Vectors
+
+- **vector:** a directed line segment  
+- arrow indicates direction
+- length indicates magnitude
+- notated as $\vec{a}, \widetilde{A}, \overrightharp{a}$
+
+
+![](graphics/vectors-intro.png)
+
+## Vector addition