Points and Vectors

1103030705

Level: 
A
Let there be a triangle KLM and vectors \( \vec{a} \), \( \vec{c} \) in the coordinate system. Triangle \( KLM \) and vectors \( \vec{a} \), \( \vec{c} \) are given in the coordinate system shown in the picture. Point T is the centroid of the triangle KLM. Express vector \( \vec{x} \), where \( \vec{x}=\overrightarrow{KT} \) as a linear combination of \( \vec{a} \) and \( \vec{c} \) and evaluate \( \left|\vec{x}\right| \).
\( \vec{x}=\frac13 \vec{a}+\frac13 \vec{c} \), \( \left|\vec{x}\right|=5 \)
\( \vec{x}=\frac23 \vec{a}+\frac23 \vec{c} \), \( \left|\vec{x}\right|=10 \)
\( \vec{x}=\frac12 \vec{a}+\frac12 \vec{c} \), \( \left|\vec{x}\right|=\frac{15}2 \)
\( \vec{x}=\frac14 \vec{a}+\frac14 \vec{c} \), \( \left|\vec{x}\right|=\frac{225}{12} \)

1103030704

Level: 
A
We are given points \( A = [2;1] \), \( B = [4;-1] \), and \( T = [6;2] \), where point \( T \) is the centroid of triangle \( ABC \). Find the length of the median of triangle \( ABC \) to side \( AC \).
\( |t_b|=\frac{\sqrt{117}}2 \)
\( |t_b|=\frac{\sqrt{45}}2 \)
\( |t_b|=\frac{\sqrt{153}}2 \)
\( |t_b|=\sqrt{117} \)

1103030701

Level: 
A
We are given points \( A = [1;-1;2] \), \( B = [0;5;-3] \), \( S = [2;0;5] \). Point \( S \) is the centre of a parallelogram \( ABCD \). Find the coordinates of vertices \( C \) and \( D \).
\( C = [3;1;8]; D = [4;-5;13] \)
\( C = [4;-5;13]; D = [3;1;8] \)
\( C = [1;1;3]; D = [2;-5;8] \)
\( C = [-3;-1;-8]; D = [-4;5;-13] \)

1003020901

Level: 
C
Let there be vectors: \(\vec{a}=(1;3;-1)\), \(\vec{b}=(0;3;1)\), \(\vec{c}=(-1;2;2)\). Find \(\vec{a}\times\vec{b}\) and \(\left(\vec{a}\times\vec{b}\right)\cdot\vec{c}\).
\(\vec{a}\times\vec{b}=(6;-1;3); \left(\vec{a}\times\vec{b}\right)\cdot\vec{c}=-2\)
\(\vec{a}\times\vec{b}=8; \left(\vec{a}\times\vec{b}\right)\cdot\vec{c}=(-8,16,16)\)
\(\vec{a}\times\vec{b}=(-6;1;-3); \left(\vec{a}\times\vec{b}\right)\cdot\vec{c}=2\)
\(\vec{a}\times\vec{b}=\sqrt{46}; \left(\vec{a}\times\vec{b}\right)\cdot\vec{c}=2\)

9000108704

Level: 
B
Consider a pair of vectors \(\vec{u} = (1;0;-1)\) and \(\vec{v} = (2;-1;1)\). Find all the vectors \(\vec{w}\) which are perpendicular to both \(\vec{u}\) and \(\vec{v}\) and satisfy \(\left |\vec{w}\right | = 2\).
\(\vec{w} = \left (\frac{2\sqrt{11}} {11} ; \frac{6\sqrt{11}} {11} ; \frac{2\sqrt{11}} {11} \right )\), \(\vec{w} = \left (-\frac{2\sqrt{11}} {11} ;-\frac{6\sqrt{11}} {11} ;-\frac{2\sqrt{11}} {11} \right )\)
\(\vec{w} = (-1;-3;-1)\), \(\vec{w} = (1;3;1)\)
\(\vec{w} = \left (-\frac{1} {2};-\frac{3} {2};-\frac{1} {2}\right )\), \(\vec{w} = \left (\frac{1} {2}; \frac{3} {2}; \frac{1} {2}\right )\)
\(\vec{w} = \left (\frac{2\sqrt{2}} {3} ; \frac{3\sqrt{2}} {2} ; \frac{2\sqrt{2}} {3} \right )\), \(\vec{w} = \left (-\frac{2\sqrt{2}} {3} ;-\frac{3\sqrt{2}} {2} ;-\frac{2\sqrt{2}} {3} \right )\)

9000108701

Level: 
B
Find all vectors which are perpendicular to the vector \(\vec{u} = (3;4)\) and have the length equal to \(1\).
\(\left (\frac{4} {5};-\frac{3} {5}\right )\), \(\left (-\frac{4} {5}; \frac{3} {5}\right )\)
\(\left (\frac{4} {7};-\frac{3} {7}\right )\), \(\left (-\frac{4} {7}; \frac{3} {7}\right )\)
\(\left ( \frac{1} {\sqrt{10}};- \frac{3} {\sqrt{10}}\right )\), \(\left (- \frac{1} {\sqrt{10}}; \frac{3} {\sqrt{10}}\right )\)
\(\left (\frac{4} {5}; \frac{3} {5}\right )\), \(\left (-\frac{4} {5};-\frac{3} {5}\right )\)