A2. The slope angle of the line $x+y-3=0$ is
(A) $45^{\circ}$
(B) $\frac{\pi}{2}$
(C) $135^{\circ}$
(D) $-60^{\circ}$
(E) other
A2. Let $\varphi$ be the inclination angle. We write the line in the form $y=3-x$. The leading coefficient is -1, so $\operatorname{tg} \varphi=-1$, from which it follows that $\varphi=135^{\circ}$.