diff --git a/src/tools/calculus.cljc b/src/tools/calculus.cljc
new file mode 100644
index 0000000..b090caf
--- /dev/null
+++ b/src/tools/calculus.cljc
@@ -0,0 +1,33 @@
+(ns tools.calculus)
+
+(defonce ^:const dx 0.0001)
+
+(defn deriv
+ "Returns the derivative of f evaluated at c. If called with only one argument,
+ it returns the derivative function."
+ ([f c]
+ ((deriv f) c))
+ ([f]
+ (fn [x]
+ (/ (- (f (+ x dx)) (f x)) dx))))
+
+(defn integrate
+ "Returns the definite integral of f over [a, b] using Simpson's method.
+ If called with only one argument (the function), returns the indefinite
+ integral, which takes as input a value x and (optionally) a constant c."
+ ([f]
+ (fn this
+ ([x] (this x 0))
+ ([x c] (+ (integrate f 0 x) c))))
+ ([f a b]
+ (let [n (/ 1 dx)
+ h (/ (- b a) n)]
+ (loop [i 1
+ sum1 (f (+ a (/ h 2)))
+ sum2 0]
+ (if (< i n)
+ (recur (inc i)
+ (+ sum1 (f (+ a (* h i) (/ h 2))))
+ (+ sum2 (f (+ a (* h i)))))
+ (* (/ h 6) (+ (f a) (f b) (* 4 sum1) (* 2 sum2))))))))
+
diff --git a/src/tools/distributions.cljc b/src/tools/distributions.cljc
new file mode 100644
index 0000000..03fbe11
--- /dev/null
+++ b/src/tools/distributions.cljc
@@ -0,0 +1,59 @@
+(ns tools.distributions
+ (:require [tools.math :as math])
+ (:require [tools.calculus :as calculus]))
+
+;; -----------------------------------------------------------------------------
+;; NORMAL
+;; -----------------------------------------------------------------------------
+
+(defn- box-muller
+ "Given two uniformly distributed random variables (from 0 to 1), returns a
+ Standard Normal variable computed using the Box-Muller Transform."
+ [u1 u2]
+ (* (math/sqrt (* -2 (math/log u1)))
+ (math/cos (* 2 math/PI u2))))
+
+(defn- normal-pdf
+ "Given a mean and standard deviation, returns the corresponding Normal
+ Probability Distribution Function."
+ [mu sigma]
+ (fn [x]
+ (* (/ 1 (* sigma (math/sqrt (* 2 math/PI))))
+ (math/exp (- (/ (math/pow (/ (- x mu) sigma) 2) 2))))))
+
+(defn rand-norm
+ "Generates n Normally-distributed random variables with given mean and
+ standard deviation. If no parameters are provided, defaults to a
+ single random observation from a Standard Normal distribution.
+ Accepts an argument map with optional keys :n, :mu, and :sigma."
+ [{:keys [n mu sigma]
+ :or {n 1, mu 0, sigma 1}}]
+ (repeatedly n #(box-muller (rand 1) (rand 1))))
+
+(defn pdf-norm
+ "Returns the value of the Normal Probability Distribution Function at a
+ particular value x. If no distributional parameters are provided, defaults to
+ the Standard Normal PDF.
+ Accepts an argument map with keys :x, and optionally :mu and :sigma."
+ [{:keys [x mu sigma]
+ :or {mu 0, sigma 1}}]
+ ((normal-pdf mu sigma) x))
+
+(defn cdf-norm
+ "Parameters: {:keys [x mu sigma]}
+ Returns the value of the Normal Cumulative Distribution Function at a
+ particular value x. If no distributional parameters are provided, defaults to
+ the Standard Normal CDF.
+ Accepts an argument map with keys :x, and optionally :mu and :sigma."
+ [{:keys [x mu sigma]
+ :or {mu 0, sigma 1}}]
+ (calculus/integrate (normal-pdf mu sigma) (- mu (* 6 sigma)) x))
+
+(defn quant-norm
+ "For a given probability p, returns the corresponding value of the quantile
+ function (i.e. the inverse Cumulative Distribution Function). If no
+ distributional parameters are provided, defaults to Standard Normal quantiles.
+ Accepts an argument map with keys :p, and optionally :mu and :sigma."
+ [{:keys [p mu sigma]
+ :or {mu 0, sigma 1}}]
+ ()) ; unfinished...
diff --git a/src/tools/math.cljc b/src/tools/math.cljc
new file mode 100644
index 0000000..91a2ae5
--- /dev/null
+++ b/src/tools/math.cljc
@@ -0,0 +1,99 @@
+(ns tools.math)
+
+(defonce PI #?(:clj Math/PI
+ :cljs js/Math.PI))
+
+(defonce E #?(:clj Math/E
+ :cljs js/Math.PI))
+
+(defn abs
+ "Returns the absolute value of a number."
+ [x]
+ (if (neg? x) (- x) x))
+
+(defn approx= [x y epsilon]
+ "Returns true if the absolute difference between x and y is less than or
+ equal to some specified error level, epsilon."
+ (<= (abs (- y x)) epsilon))
+
+(defn ceil
+ "Returns the smallest integer greater than or equal to x."
+ [x]
+ #?(:clj (Math/ceil x)
+ :cljs (js/Math.ceil x)))
+
+(defn cos
+ "Returns the cosine of an angle (specified in radians)."
+ [x]
+ #?(:clj (Math/cos x)
+ :cljs (js/Math.cos x)))
+
+(defn exp
+ "Returns Euler's number (approx. 2.71) raised to the given power."
+ [x]
+ #?(:clj (Math/exp x)
+ :cljs (js/Math.exp x)))
+
+(defn floor
+ "Returns the largest integer less than or equal to x."
+ [x]
+ #?(:clj (Math/floor x)
+ :cljs (js/Math.floor x)))
+
+(defn log
+ "Returns the logarithm of x with the given base. If called with only one
+ argument, returns the natural logarithm (base e) of the given value."
+ ([x base]
+ (/ (log x) (log base)))
+ ([x]
+ #?(:clj (Math/log x)
+ :cljs (js/Math.log x))))
+
+(defn pow
+ "Returns the value obtained by raising the first argument to the power of
+ the second argument."
+ [x n]
+ #?(:clj (Math/pow x n)
+ :cljs (js/Math.pow x n)))
+
+(defn root
+ "Returns the root of x with base n."
+ [x n]
+ (pow x (/ 1 n)))
+
+(defn round
+ "Returns the value of x rounded to the nearest integer."
+ [x]
+ #?(:clj (Math/round x)
+ :cljs (js/Math.round x)))
+
+(defn sign
+ "Returns the 1 if the argument is positive, -1 if the argument is negative,
+ and 0 if the argument is zero."
+ [x]
+ (cond (< x 0) -1
+ (> x 0) 1
+ :else 0))
+
+(defn sin
+ "Returns the sine of an angle (specified in radians)."
+ [x]
+ #?(:clj (Math/sin x)
+ :cljs (js/Math.sin x)))
+
+(defn sqrt
+ "Returns the square root of the given value."
+ [x]
+ #?(:clj (Math/sqrt x)
+ :cljs (js/Math.sqrt x)))
+
+(defn square
+ "Returns the square of the given value."
+ [x]
+ (* x x))
+
+(defn tan
+ "Returns the tangent of an angle (specified in radians)."
+ [x]
+ #?(:clj (Math/tan x)
+ :cljs (js/Math.tan x)))