The differential equation whose solution is $\mathrm{A} x^2+\mathrm{B} y^2=1$, where A and B are arbitrary constants is of

The angle between the lines $x=y, z=0$ and $y=0, \mathrm{z}=0$ is

Let $\bar{a}, \bar{b}, \bar{c}$ be three vectors such that $\overline{\mathrm{a}}+\overline{\mathrm{b}}+\overline{\mathrm{c}}=\overline{0},|\overline{\mathrm{a}}|=3,|\overline{\mathrm{~b}}|=4,|\overline{\mathrm{c}}|=5$, then $\overline{\mathrm{a}} \cdot \overline{\mathrm{b}}+\overline{\mathrm{b}} \cdot \overline{\mathrm{c}}+\overline{\mathrm{c}} \cdot \overline{\mathrm{a}}=$

The area bounded by the curve $y=x^2+3, y=x, x=3$ and $y$-axis is