Points and vectors

1103024302

Level: 
A
In a regular hexagon \( ABCDEF \) shown in the picture, let \( \overrightarrow{a} = \overrightarrow{AB} \), \( \overrightarrow{b} = \overrightarrow{BC} \), \( \overrightarrow{c} = \overrightarrow{FD} \) and \( \overrightarrow{d} = \overrightarrow{CD} \). Express vectors \( \overrightarrow{c} \) and \( \overrightarrow{d} \) as a linear combination of vectors \( \overrightarrow{a} \) and \( \overrightarrow{b} \).
\( \overrightarrow{c} = \overrightarrow{a} + \overrightarrow{b};\ \overrightarrow{d} = \overrightarrow{b} - \overrightarrow{a} \)
\( \overrightarrow{c} = 2\overrightarrow{a} + 2\overrightarrow{b};\ \overrightarrow{d} = 2\overrightarrow{b} - 0.5\overrightarrow{a} \)
\( \overrightarrow{c} = 2\overrightarrow{a} + \overrightarrow{b};\ \overrightarrow{d} = \overrightarrow{b} - \overrightarrow{a} \)
\( \overrightarrow{c} = \overrightarrow{a} + \overrightarrow{b};\ \overrightarrow{d} = \overrightarrow{a} - \overrightarrow{b} \)

1103024301

Level: 
A
In a triangle \( ABC \), let \( K \), \( L \) and \( M \) be the midpoints of \( AB \), \( BC \) and \( AC \) consecutively and let \( T \) be the centroid of \( ABC \). Find the values of coefficients \( k \), \( l \) and \(m \) if: \[ \overrightarrow{TM} = k\cdot\overrightarrow{BT};\ \overrightarrow{ML} = l\cdot\overrightarrow{BA};\ \overrightarrow{CK} = m\cdot\overrightarrow{TC} \]
\( k=\frac12;\ l=-\frac12 ;\ m=-\frac32 \)
\( k=\frac12;\ l=\frac12;\ m=-\frac32 \)
\( k=\frac12 ;\ l=-\frac12 ;\ m=-\frac23 \)
\( k=\frac12;\ l=-\frac12;\ m=\frac32 \)

1103021001

Level: 
B
Let \( ABCDEF \) be a regular hexagon with the centre \( S \) and the side of length \( 3\,\mathrm{cm}\). The point \( G \) is the midpoint of the segment \( AB \). The vectors \( \overrightarrow{u} \), \( \overrightarrow{v} \), \( \overrightarrow{w} \), \( \overrightarrow{z} \) are indicated in the hexagon shown in the picture. Find the dot product of: \( \overrightarrow{v}\cdot\overrightarrow{w} \), \( \overrightarrow{v}\cdot\overrightarrow{z} \) and \( \overrightarrow{v}\cdot\overrightarrow{u} \).
\( \overrightarrow{v}\cdot\overrightarrow{w}=9 \), \( \overrightarrow{v}\cdot\overrightarrow{z} = 0 \), \( \overrightarrow{v}\cdot\overrightarrow{u}=27 \)
\( \overrightarrow{v}\cdot\overrightarrow{w}=9 \), \( \overrightarrow{v}\cdot\overrightarrow{z} = 0 \), \( \overrightarrow{v}\cdot\overrightarrow{u}=9\sqrt6 \)
\( \overrightarrow{v}\cdot\overrightarrow{w}=\frac92 \), \( \overrightarrow{v}\cdot\overrightarrow{z} = 0 \), \( \overrightarrow{v}\cdot\overrightarrow{u}=9\sqrt6 \)
\( \overrightarrow{v}\cdot\overrightarrow{w}=\frac92 \), \( \overrightarrow{v}\cdot\overrightarrow{z} = 1 \), \( \overrightarrow{v}\cdot\overrightarrow{u}=27 \)

1103030705

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

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: \(\overrightarrow{a}=(1;3;-1)\), \(\overrightarrow{b}=(0;3;1)\), \(\overrightarrow{c}=(-1;2;2)\). Find \(\overrightarrow{a}\times\overrightarrow{b}\) and \(\left(\overrightarrow{a}\times\overrightarrow{b}\right)\cdot\overrightarrow{c}\).
\(\overrightarrow{a}\times\overrightarrow{b}=(6;-1;3); \left(\overrightarrow{a}\times\overrightarrow{b}\right)\cdot\overrightarrow{c}=-2\)
\(\overrightarrow{a}\times\overrightarrow{b}=8; \left(\overrightarrow{a}\times\overrightarrow{b}\right)\cdot\overrightarrow{c}=(-8,16,16)\)
\(\overrightarrow{a}\times\overrightarrow{b}=(-6;1;-3); \left(\overrightarrow{a}\times\overrightarrow{b}\right)\cdot\overrightarrow{c}=2\)
\(\overrightarrow{a}\times\overrightarrow{b}=\sqrt{46}; \left(\overrightarrow{a}\times\overrightarrow{b}\right)\cdot\overrightarrow{c}=2\)