update methods / physics / spec notes

diff --git a/methods/calculus.md b/methods/calculus.md
index 8cb35215e73c998d11398ef33a8a1502f916203c..fb3761fef5a7f5d388d3a3c9322bb385104516c3 100644 (file)
--- a/methods/calculus.md
+++ b/methods/calculus.md
@@ -72,3 +72,8 @@ Normal line for point $P(q,r)$ on function $f$ is $y=mx+c$ where $m={-1 \over m_
 
 **In main**: type function. Interactive -> Calculation -> Line -> (Normal | Tan line)  
 **In graph**: define function. Analysis -> Sketch -> (Normal | Tan line). Type $x$ value to solve for a point. Return to show equation for line.
+
+## Stationary points
+
+Stationary where $m=0$.  
+Find derivative, solve for ${dy \over dx} = 0$