This exercise is a multiple choice questionnaire. For each of the following questions, only one of the four proposed answers is correct.
A correct answer earns one point. An incorrect answer, a multiple answer, or the absence of an answer to a question earns neither points nor deducts points. To answer, indicate on your paper the question number and the letter of the chosen answer. No justification is required.
SABCD is a regular pyramid with square base ABCD in which all edges have the same length. The point I is the center of the square ABCD. We assume that: $\mathrm{IC} = \mathrm{IB} = \mathrm{IS} = 1$. The points K, L and M are the midpoints of edges [SD], [SC] and [SB] respectively.
- The following lines are not coplanar: a. (DK) and (SD) b. (AS) and (IC) c. (AC) and (SB) d. (LM) and (AD)
For the following questions, we place ourselves in the orthonormal coordinate system of space $(\mathrm{I}; \overrightarrow{\mathrm{IC}}, \overrightarrow{\mathrm{IB}}, \overrightarrow{\mathrm{IS}})$. In this coordinate system, we are given the coordinates of the following points: $$\mathrm{I}(0;0;0) \quad ; \quad \mathrm{A}(-1;0;0) \quad ; \quad \mathrm{B}(0;1;0) \quad ; \quad \mathrm{C}(1;0;0) \quad ; \quad \mathrm{D}(0;-1;0) \quad ; \quad \mathrm{S}(0;0;1).$$
\setcounter{enumi}{1} - The coordinates of the midpoint N of [KL] are: a. $\left(\frac{1}{4};\frac{1}{4};\frac{1}{4}\right)$ b. $\left(\frac{1}{4};-\frac{1}{4};\frac{1}{2}\right)$ c. $\left(-\frac{1}{4};\frac{1}{4};\frac{1}{2}\right)$ d. $\left(-\frac{1}{2};\frac{1}{2};1\right)$
- The coordinates of the vector $\overrightarrow{\mathrm{AS}}$ are: a. $\left(\begin{array}{l}1\\1\\0\end{array}\right)$ b. $\left(\begin{array}{l}1\\0\\1\end{array}\right)$ c. $\left(\begin{array}{c}2\\1\\-1\end{array}\right)$ d. $\left(\begin{array}{l}1\\1\\1\end{array}\right)$
- A parametric representation of the line (AS) is: a. $\left\{\begin{array}{rl}x &= -1-t\\y &= t\\z &= -t\end{array}\right.$ b. $\left\{\begin{aligned}x =& -1+2t\\y =& 0\\z =& 1+2t\end{aligned}\right.$ c. $\left\{\begin{aligned}x &= t\\y &= 0\\z &= 1+t\end{aligned}\right.$ d. $\left\{\begin{aligned}x &= -1-t\\y &= 1+t\\z &= 1-t\end{aligned}\right. (t \in \mathbb{R})$
- A Cartesian equation of the plane (SCB) is: a. $y+z-1=0$ b. $x+y+z-1=0$ c. $x-y+z=0$ d. $x+z-1=0$