$𝑎=𝑏$ $$\left(\begin{array}{ccc}1& 0& 0\\ 0& 1& 0\\ 0& 0& 1\end{array}\right)=\{\begin{array}{cc}1\hfill & \text{if <math xmlns="http://www.w3.org/1998/Math/MathML"> <mi>𝑎</mi> <mo lspace="0.278em" rspace="0.278em">=</mo> <mi>𝑏</mi> </math>}\hfill \\ 2\hfill & \text{else}\hfill \end{array}$$ $$𝑥=\frac{-𝑏\pm \sqrt{{𝑏}^2-4𝑎𝑐}}{2𝑎}.$$ $𝑏$ $$\sum _{𝑎}\underset{\_}{𝑐}\stackrel{\_}{𝑏}{𝑐}^{\mathrm{\prime }}$$ $\sin (𝑥)-\sin (𝑥+2𝜋)=0$