When \(a \ne 0\), there are two solutions to \(ax^2 + bx + c = 0\) and they are
$$x = {-b \pm \sqrt{b^2-4ac} \over 2a}.$$
\(dt(X,Y)=2\theta g(\phi X,Y)\) 은 "East Asian Mathematical Journal"의 논문 "Semi-invarinat Submanifolds of Codimension 3 satisfying \(\nabla_{\phi\nabla_{\xi}\xi}R_\xi =0\) in a Complex Space Form"에 나온 수식이다.
$$R =\bigoplus_{\alpha \in \Gamma}R_{\alpha}$$
$$E=mc^2$$