Math: document the usual notation for complex/dual/quat numbers.

src/Magnum/Math/Complex.h

@@ -79,7 +79,13 @@ template<class T> inline Rad<T> angle(const Complex<T>& normalizedA, const Compl
 @brief Complex number
 @tparam T   Data type
 
-Represents 2D rotation. See @ref transformations for brief introduction.
+Represents 2D rotation. Usually denoted as the following in equations, with
+@f$ a_0 @f$ being the @ref real() part and @f$ a_i @f$ the @ref imaginary()
+part: @f[
+    c = a_0 + i a_i
+@f]
+
+See @ref transformations for brief introduction.
 @see @ref Magnum::Complex, @ref Magnum::Complexd, @ref Matrix3
 */
 template<class T> class Complex {
@@ -191,11 +197,11 @@ template<class T> class Complex {
             return Implementation::isNormalizedSquared(dot());
         }
 
-        /** @brief Real part */
+        /** @brief Real part (@f$ a_0 @f$) */
         T& real() { return _real; }
         constexpr T real() const { return _real; } /**< @overload */
 
-        /** @brief Imaginary part */
+        /** @brief Imaginary part (@f$ a_i @f$) */
         T& imaginary() { return _imaginary; }
         constexpr T imaginary() const { return _imaginary; } /**< @overload */
 

src/Magnum/Math/Dual.h

@@ -45,6 +45,11 @@ namespace Implementation {
 /**
 @brief Dual number
 @tparam T   Underlying data type
+
+Usually denoted as the following in equations, with @f$ a_0 @f$ being the
+@ref real() part and @f$ a_\epsilon @f$ the @ref dual() part: @f[
+    \hat a = a_0 + \epsilon a_\epsilon
+@f]
 */
 template<class T> class Dual {
     template<class> friend class Dual;
@@ -121,13 +126,13 @@ template<class T> class Dual {
             return !operator==(other);
         }
 
-        /** @brief Real part */
+        /** @brief Real part (@f$ a_0 @f$) */
         T& real() { return _real; }
         /* Returning const so it's possible to call constexpr functions on the
            result. WTF, C++?! */
         constexpr const T real() const { return _real; } /**< @overload */
 
-        /** @brief Dual part */
+        /** @brief Dual part (@f$ a_\epsilon @f$) */
         T& dual() { return _dual; }
         /* Returning const so it's possible to call constexpr functions on the
            result. WTF, C++?! */

src/Magnum/Math/DualComplex.h

@@ -43,8 +43,14 @@ namespace Implementation {
 @brief Dual complex number
 @tparam T   Underlying data type
 
-Represents 2D rotation and translation. See @ref transformations for brief
-introduction.
+Represents 2D rotation and translation. Usually denoted as the following in
+equations, with @f$ q_0 @f$ being the @ref real() part and @f$ q_\epsilon @f$
+the @ref dual() part: @f[
+    \hat q = q_0 + \epsilon q_\epsilon
+@f]
+
+See @ref Dual and @ref Complex for further notation description and
+@ref transformations for brief introduction.
 @see @ref Magnum::DualComplex, @ref Magnum::DualComplexd, @ref Dual,
     @ref Complex, @ref Matrix3
 @todo Can this be done similarly as in dual quaternions? It sort of works, but

src/Magnum/Math/DualQuaternion.h

@@ -179,8 +179,14 @@ template<class T> inline DualQuaternion<T> sclerpShortestPath(const DualQuaterni
 @brief Dual quaternion
 @tparam T   Underlying data type
 
-Represents 3D rotation and translation. See @ref transformations for brief
-introduction.
+Represents 3D rotation and translation. Usually denoted as the following in
+equations, with @f$ q_0 @f$ being the @ref real() part and @f$ q_\epsilon @f$
+the @ref dual() part: @f[
+    \hat q = q_0 + \epsilon q_\epsilon
+@f]
+
+See @ref Dual and @ref Quaternion for further notation description and
+@ref transformations for a brief introduction.
 @see @ref Magnum::DualQuaternion, @ref Magnum::DualQuaterniond, @ref Dual,
     @ref Quaternion, @ref Matrix4
 */

src/Magnum/Math/Quaternion.h

@@ -333,13 +333,13 @@ template<class T> class Quaternion {
             return Implementation::isNormalizedSquared(dot());
         }
 
-        /** @brief Vector part */
+        /** @brief Vector part (@f$ \boldsymbol{q}_V @f$) */
         Vector3<T>& vector() { return _vector; }
         /* Returning const so it's possible to call constexpr functions on the
            result. WTF, C++?! */
         constexpr const Vector3<T> vector() const { return _vector; } /**< @overload */
 
-        /** @brief Scalar part */
+        /** @brief Scalar part (@f$ q_S @f$) */
         T& scalar() { return _scalar; }
         constexpr T scalar() const { return _scalar; } /**< @overload */