\form#0:$\mbox{\LaTeX}$
\form#1:$\mbox{\TeX}$
\form#2:$(x_1,y_1)$
\form#3:$(x_2,y_2)$
\form#4:$\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}$
\form#5:\[ |I_2|=\left| \int_{0}^T \psi(t) \left\{ u(a,t)- \int_{\gamma(t)}^a \frac{d\theta}{k(\theta,t)} \int_{a}^\theta c(\xi)u_t(\xi,t)\,d\xi \right\} dt \right| \]