calculus ref for methods

diff --git a/methods/calculus.md b/methods/calculus.md
index c28a4984c384a834a0888aeaa0e38bd366217e9b..8824f9c1d65b04fbf6a12ad8f35f94f053f898fc 100644 (file)
--- a/methods/calculus.md
+++ b/methods/calculus.md
@@ -53,6 +53,8 @@ $$f^\prime(x)=\lim_{h \rightarrow 0}{{f(x+h)-f(x)} \over h}$$
 
 **Tangent line** of function $f$ at point $M(a, f(a))$ is the line through $M$ with gradient $f^\prime(a)$.
 
+For $f(x)=x^n, \hspace{0.5em} f^\prime (x) = nx^{n-1}$
+
 ## Tangents and gradients