New
New
Year 11
Higher

Geometric proofs with vectors

I can produce geometric proofs to prove that points are collinear or that vectors are parallel.

New
New
Year 11
Higher

Geometric proofs with vectors

I can produce geometric proofs to prove that points are collinear or that vectors are parallel.

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Lesson details

Key learning points

  1. Your knowledge of the properties of polygons can be applied to vector problems.
  2. A regular polygon has a relationship between sides that can be represented with vector notation.
  3. Your knowledge can be used to identify vectors and multiples of known vectors.
  4. Through manipulation, you can prove certain properties.

Keywords

  • Collinear - When three or more points lie on a single straight line, these points are said to be collinear.

Common misconception

When calculating the resultant vector, pupils can incorrectly sum vectors due to opposite directions or proportions of vectors.

Encourage pupils to write a clear vector pathway, sometimes using highlighters can help visualise this pathway.

For greater challenge, describe a vector diagram using vertices, algebraic vectors and proportions. Do not provide a diagram. Using algebraic terms and pupils must draw the vector diagram and prove what is required.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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6 Questions

Q1.
Work out the magnitude of the vector $${4 \choose -3}$$.
Correct Answer: 5, 5 cm, 5 units
Q2.
Which of the following vectors are parallel to $$2\mathbf{a}-3\mathbf{b}$$?
$$4\mathbf{a}-1\mathbf{b}$$
$$6\mathbf{a}-4\mathbf{b}$$
Correct answer: $$4\mathbf{a}-6\mathbf{b}$$
Correct answer: $$-10\mathbf{a}+15\mathbf{b}$$
Q3.
Which of the following vectors are parallel to $${8\choose -12}$$?
Correct answer: $${4\choose -6}$$
Correct answer: $${-4\choose 6}$$
$${-3\choose2}$$
$${24\choose 36}$$
Correct answer: $${0.8\choose -1.2}$$
Q4.
X is a point on the line AB. Match each vector statement to the correct ratio.
Correct Answer:AX : XB is 1 : 4,$$\frac{1}{5}\overrightarrow{AB}=\overrightarrow{AX}$$

$$\frac{1}{5}\overrightarrow{AB}=\overrightarrow{AX}$$

Correct Answer:AX : XB is 3 : 8,$$\frac{3}{11}\overrightarrow{AB}=\overrightarrow{AX}$$

$$\frac{3}{11}\overrightarrow{AB}=\overrightarrow{AX}$$

Correct Answer:AX : XB is 1 : 1,$$\frac{1}{2}\overrightarrow{AB}=\overrightarrow{AX}$$

$$\frac{1}{2}\overrightarrow{AB}=\overrightarrow{AX}$$

Correct Answer:AX : XB is 3 : 1,$$\frac{3}{4}\overrightarrow{AB}=\overrightarrow{AX}$$

$$\frac{3}{4}\overrightarrow{AB}=\overrightarrow{AX}$$

Q5.
Match each value of $$x$$ to the vector equation that it satisfies.
Correct Answer:$$x = 13$$ ,$${x \choose -2} + {12 \choose 7} = {25 \choose 5} $$

$${x \choose -2} + {12 \choose 7} = {25 \choose 5} $$

Correct Answer:$$x=12$$ ,$${x\choose -7} + {-7 \choose -7} = {5 \choose -14} $$

$${x\choose -7} + {-7 \choose -7} = {5 \choose -14} $$

Correct Answer:$$x=4$$ ,$$x{2 \choose 8} = {8 \choose 32} $$

$$x{2 \choose 8} = {8 \choose 32} $$

Correct Answer:$$x=8$$ ,$$3{3\choose 4} + {3 \choose -4} = {12 \choose x} $$

$$3{3\choose 4} + {3 \choose -4} = {12 \choose x} $$

Q6.
OACB is a parallelogram. M is the midpoint of OA and N is the midpoint of OB. $$\overrightarrow{OM}=2\mathbf{a}$$ and $$\overrightarrow{ON}=2\mathbf{b}$$.
Correct answer: $$\frac{1}{2}\overrightarrow{AB}=\overrightarrow{MN}$$
$$\overrightarrow{MN}=2\overrightarrow{AB}$$
$$\frac{1}{3}\overrightarrow{AB}=\overrightarrow{MN}$$
Correct answer: $$2\overrightarrow{MN}=\overrightarrow{AB}$$
$$\overrightarrow{AB}=\frac{1}{2}\overrightarrow{MN}$$

6 Questions

Q1.
Three points that lie along the same straight line are said to be .
Correct Answer: collinear
Q2.
Select the correct statements to show that $$ODEF$$ is a trapezium.
An image in a quiz
$$\overrightarrow{OD}=2\overrightarrow{EF}$$
Correct answer: $$\overrightarrow{OD}=2\overrightarrow{FE}$$
$$\overrightarrow{OD}=\frac{1}{2}\overrightarrow{FE}$$
$$\overrightarrow{OF}=k\overrightarrow{ED}$$
Correct answer: $$\overrightarrow{OF}\neq k\overrightarrow{ED}$$
Q3.
Select the correct statements to show that $$OAEF$$ is not a parallelogram.
An image in a quiz
$$\overrightarrow{OF}=\overrightarrow{AE}$$
$$\overrightarrow{OF}=2\overrightarrow{AE}$$
Correct answer: $$2\overrightarrow{OF}=\overrightarrow{AE}$$
$$\overrightarrow{OA}=\overrightarrow{FE}$$
Correct answer: $$\overrightarrow{OA}\neq k\overrightarrow{FE}$$
Q4.
$$ABCD$$ is a kite. $$W,X,Y,Z$$ are midpoints of the lines they lie on. $$\overrightarrow{XW} = k(\mathbf b - \mathbf a)$$ where $$k= $$
An image in a quiz
Correct Answer: 2
Q5.
$$ABCD$$ is a kite. $$W,X,Y,Z$$ are midpoints of the lines they lie on. Find $$\overrightarrow{ZW}$$.
An image in a quiz
$$- \mathbf c - \mathbf b$$
Correct answer: $$-2 \mathbf c -2 \mathbf b$$
$$2\mathbf c + 2\mathbf b$$
$$\mathbf c + \mathbf b$$
Q6.
$$ABCD$$ is a kite. $$W,X,Y,Z$$ are midpoints of the lines they lie on. Find $$\overrightarrow{XZ}$$.
An image in a quiz
$$- \mathbf c - 2\mathbf b + \mathbf a$$
$$ \mathbf c + 2\mathbf b - \mathbf a$$
$$-2 \mathbf c -4 \mathbf b + 2\mathbf a$$
Correct answer: $$ 2\mathbf c + 4\mathbf b - 2\mathbf a$$