∫−∞+∞e−x2dx=π\int_{-\infty}^{+\infty} e^{-x^2} dx = \sqrt{\pi} ∫−∞+∞ e−x2dx=π
{ utt(x,t)=b(t)△u(x,t−4) −q(x,t)f[u(x,t−3)]+te−tsin2x,t≠tk; u(x,tk+)−u(x,tk−)=cku(x,tk),k=1,2,3…; ut(x,tk+)−ut(x,tk−)=ckut(x,tk),k=1,2,3… .\begin{cases} \ u_{tt}(x,t)= b(t)\triangle u(x,t-4)&\\ \ \hspace{42pt}- q(x,t)f[u(x,t-3)]+te^{-t}\sin^2 x, & t \neq t_k; \\ \ u(x,t_k^+) - u(x,t_k^-) = c_k
u(x,t_k), & k=1,2,3\ldots ;\\ \ u_{t}(x,t_k^+) - u_{t}(x,t_k^-) =c_k u_{t}(x,t_k), & k=1,2,3\ldots\ . \end{cases} ⎩⎨⎧ utt (x,t)=b(t)△u(x,t−4) −q(x,t)f[u(x,t−3)]+te−tsin2x, u(x,tk+ )−u(x,tk− )=ck u(x,tk ), ut (x,tk+ )−ut (x,tk− )=ck ut (x,tk ), t=tk ;k=1,2,3…;k=1,2,3… .
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> 这是一个引用。
E=mc2E = mc^2E=mc2
E=mc2E = mc^2 E=mc2
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