[spec] rational functions

diff --git a/spec/calculus.md b/spec/calculus.md
index c59c4b77e306241793268f6d18b4bd26c6efdf7e..c9a364ecccf46203cc9bceead47d6de55afbd881 100644 (file)
--- a/spec/calculus.md
+++ b/spec/calculus.md
@@ -257,3 +257,13 @@ $${dy \over dx} = {{dy \over dt} \over {dx \over dt}} \> \vert \> {dx \over dt}
 
 $${d^2 \over dx^2} = {d(y^\prime) \over dx} = {{dy^\prime \over dt} \over {dx \over dt}} \> \vert \> y^\prime = {dy \over dx}$$
 
 
 $${d^2 \over dx^2} = {d(y^\prime) \over dx} = {{dy^\prime \over dt} \over {dx \over dt}} \> \vert \> y^\prime = {dy \over dx}$$
 

+# Rational functions
+
+$$f(x) = {P(x) \over Q(x)} \quad \text{where } P, Q \text{ are polynomial functions}$$
+
+## Addition of ordinates
+
+- when two graphs have the same ordinate, $y$-coordinate is double the ordinate
+- when two graphs have opposite ordinates, $y$-coordinate is 0 i.e. ($x$-intercept)
+- when one of the ordinates is 0, the resulting ordinate is equal to the other ordinate
+