Math: mention more useful dot product and determinant properties.

src/Magnum/Math/Matrix.h

@@ -163,7 +163,8 @@ template<std::size_t size, class T> class Matrix: public RectangularMatrix<size,
         /**
          * @brief Determinant
          *
-         * Computed recursively using Laplace's formula: @f[
+         * Returns `0` if the matrix is noninvertible and `1` if the matrix is
+         * orthogonal. Computed recursively using Laplace's formula: @f[
          *      \det(A) = \sum_{j=1}^n (-1)^{i+j} a_{i,j} \det(A^{i,j})
          * @f] @f$ A^{i, j} @f$ is matrix without i-th row and j-th column, see
          * @ref ij(). The formula is expanded down to 2x2 matrix, where the

src/Magnum/Math/Vector.h

@@ -73,8 +73,10 @@ namespace Implementation {
 /** @relatesalso Vector
 @brief Dot product of two vectors
 
-Returns `0` when two vectors are perpendicular, `1` when two *normalized*
-vectors are parallel and `-1` when two *normalized* vectors are antiparallel. @f[
+Returns `0` when two vectors are perpendicular, `> 0` when two vectors are in
+the same general direction, `1` when two *normalized* vectors are parallel,
+`< 0` when two vectors are in opposite general direction and `-1` when two
+*normalized* vectors are antiparallel. @f[
     \boldsymbol a \cdot \boldsymbol b = \sum_{i=0}^{n-1} \boldsymbol a_i \boldsymbol b_i
 @f]
 @see @ref Vector::dot() const, @ref Vector::operator-(), @ref Vector2::perpendicular()