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Edexcel International GCSE Maths A (4MA1) · Vectors & Transformation Geometry
Mini-Lesson

Vectors & Transformation Geometry

This mini-lesson covers the whole of the Edexcel 4MA1 topic: the four transformations (reflection, rotation, translation, enlargement), how to describe, combine and spot invariant points, then column vectors, their magnitude, arithmetic, and vector geometry proofs.

object transform image vector a length + direction

Work through each screen, answer the questions (some are calculations, some concept checks) and collect ⭐ stars. Screens tagged Higher are Higher-tier only. Press Start.

Setting the scene

Object, image & the coordinate grid

A transformation maps an object onto an image. The image is often labelled with dashes, e.g. triangle A → triangle A′. Edexcel 4MA1 needs you to carry out and fully describe four transformations:

  • Reflection — in a mirror line
  • Rotation — about a centre, through an angle, in a direction
  • Translation — by a column vector
  • Enlargement — from a centre, by a scale factor

Key idea: reflection, rotation and translation keep the shape the same size (congruent). Only enlargement changes the size (similar shapes).

Transformation 1

Reflection

A reflection flips a shape across a mirror line. Every point moves to the opposite side of the line, the same distance away. To describe one fully you must give the equation of the mirror line (e.g. x = 0, y = 2, y = x).

mirror x = 0 A A′
Reflecting triangle A in the y-axis (x = 0). The mirror line is unchanged, so points on it are invariant.
Worked example — coordinates

Reflect the point (2, 3) in the x-axis (the line y = 0).

The x-coordinate stays; the y-coordinate flips sign: (2, 3) → (2, −3).

Quick check

Reflect in y = x

?The point (2, 5) is reflected in the line y = x. What are the coordinates of its image?
Transformation 2

Rotation

A rotation turns a shape about a fixed point. To describe one fully you need three things:

  • the centre of rotation (e.g. the origin, or (1, 2))
  • the angle (usually 90°, 180° or 270°)
  • the direction — clockwise or anticlockwise
O A A′ 90° CW
Rotating A by 90° clockwise about the origin O. A point (x, y) maps to (y, −x).

Misconception: saying "rotate 90°" is not enough. Without the centre, the angle and the direction, the description is incomplete and loses marks.

Quick check

Describe the rotation

?Which of these is a complete description of a rotation?
Transformation 3

Translation by a column vector

A translation slides a shape without turning or resizing it. It is described by a column vector a
b
where the top number is the movement in x (right +) and the bottom number is the movement in y (up +).

A A′ 4 right, 2 down
Translation by 4
−2
: 4 to the right, 2 down.
Worked example

Translate (1, 1) by the vector 4
−2
.

Add the vector to the point: (1 + 4, 1 + (−2)) = (5, −1).

Misconception: the column vector is top = x, bottom = y — never the other way round. And to reverse a translation you negate both numbers.

Calculate

Your turn — translate a point

1The point (3, 4) is translated by the column vector −5
2
. What is the x-coordinate of the image?
(x)
Hint: new x = 3 + (−5).
Transformation 4

Enlargement from a centre

An enlargement changes the size of a shape. Describe it with a centre of enlargement and a scale factor (SF). Each point moves so its distance from the centre is multiplied by the SF.

C A A′ SF = 2
Enlargement, scale factor 2, centre C. Ray lines from C through each vertex fix the image. Each side of A′ is twice as long.
Worked example — SF from centre O

Enlarge the point (2, 1) by scale factor 3, centre the origin.

Multiply each coordinate by the SF: (2 × 3, 1 × 3) = (6, 3).

Enlargement · special scale factors

Fractional & negative scale factors

The scale factor need not be a whole number bigger than 1:

  • SF > 1 → image is bigger (e.g. SF 2, SF 3).
  • 0 < SF < 1 (fractional) → image is smaller, e.g. SF ½ halves every distance. It is still called an enlargement.
  • Negative SF → image is on the opposite side of the centre and turned upside-down (Higher-tier practice).
C A A′ SF = ½
Scale factor ½ from centre C: the image A′ is smaller but still an enlargement.

Misconception: a scale factor less than 1 does not mean "no enlargement" — it just makes the image smaller. And a negative SF flips the shape to the other side of the centre; it is not the same as making it smaller.

Calculate

Your turn — enlarge a point

2The point (8, 6) is enlarged by scale factor ½, centre the origin. What is the y-coordinate of the image?
(y)
Hint: multiply the y-coordinate by ½: 6 × ½.
Higher · Quick check

Negative scale factor

?The point (2, 1) is enlarged by scale factor −1, centre the origin. Where does it map to?
Describing & combining

Describe fully, and combine

When asked to describe fully, name the single transformation and give all its details:

  • Reflection → equation of mirror line.
  • Rotation → centre, angle, direction.
  • Translation → column vector.
  • Enlargement → centre and scale factor.

You may also do two transformations one after another (a combination). The result can sometimes be described as a single transformation.

Exam tip: if a question says "describe the single transformation", one word (like "reflection") on its own scores nothing — you must add the full details, and never describe it as two transformations.

Invariance

Invariant points

A point is invariant if it stays exactly where it is after a transformation.

  • Reflection: points on the mirror line are invariant.
  • Rotation: the centre of rotation is invariant.
  • Enlargement: the centre of enlargement is invariant.
  • Translation: no invariant points (everything moves) unless the vector is zero.
mirror line invariant points
Under reflection, only points lying on the mirror line are invariant.
Sort it

Which transformation?

Read each clue and tap the transformation it describes.

Match up

Transformation ↔ what you must state

Tap a transformation on the left, then its required description on the right.

Transformation
You must give…
Higher · Vectors

What is a vector?

A vector has both magnitude (length) and direction. We write it as a column vector x
y
: top = movement in x, bottom = movement in y. Vectors are printed in bold (a) or underlined (a).

3 across 4 up a
The vector a = 3
4
: 3 to the right and 4 up.
Higher · Vectors

Magnitude (modulus) of a vector

The magnitude (or modulus) is the vector's length. Using Pythagoras on the x- and y-parts:

|a| = √(x² + y²)magnitude = square root of (x-part² + y-part²)
Worked example

Find the magnitude of a = 3
4
.

|a| = √(3² + 4²) = √(9 + 16) = √25 = 5.

This is a 3–4–5 triangle. A vector and its reverse (e.g. 3
4
and −3
−4
) have the same magnitude.

Calculate

Your turn — magnitude

3Find the magnitude of the vector 5
12
.
units
Hint: √(5² + 12²) = √(25 + 144).
Higher · Vectors

Adding & subtracting vectors

Add or subtract vectors component by component — top with top, bottom with bottom:

2
3
+ 3
−1
= 5
2
2+3 = 5 (top), 3+(−1) = 2 (bottom)

Geometrically, a + b means "do a, then b" — placing them nose-to-tail. The single vector from start to finish is the resultant.

a b a + b
Nose-to-tail: a then b. The green resultant is a + b.
Higher · Vectors

Scalar multiples & −a

Multiplying a vector by a scalar (a number) multiplies both components:

32
−1
= 6
−3
each part × 3

A scalar multiple like 3a is parallel to a (same direction, 3× as long). The vector −a has the same length but points the opposite way.

a −a
−a is the same length as a but reversed in direction.

Misconception: −a is not a shrunk version of a — it is the same length, opposite direction. Only a scalar between −1 and 1 changes the length.

Calculate

Your turn — vector arithmetic

4Given a = 3
−2
, work out the top component of 2a.
(top)
Hint: 2 × 3 for the top component.
Higher · Vectors

Position vectors

The position vector of a point A is the vector from the origin O to A, written OA (with an arrow above) or a. To go from A to B:

AB = bavector A→B = (position of B) − (position of A)

So you always do "finish minus start". This is the key to every vector-geometry proof.

Worked example

A has position vector 1
2
, B has position vector 4
7
.

AB = ba = 4
7
1
2
= 3
5
.

Higher · Vectors

Vector geometry proofs

Exam proofs usually ask you to show two vectors are parallel or that points are collinear (in a straight line). The trick:

  • Write the vectors you need using "finish − start".
  • If one vector is a scalar multiple of another (e.g. PQ = 2RS), they are parallel.
  • If two such vectors share a point and are parallel, the points are collinear.
Worked example — parallel

Suppose PQ = 2
3
and RS = 4
6
.

RS = 2 × 2
3
= 2PQ. Since RS is a scalar multiple of PQ, PQ is parallel to RS (and twice as long).

Higher · Quick check

Are they parallel?

?Vector u = 2
−1
and vector v = −6
3
. Which statement is true?
Recap

What you must know

Reflection: give the mirror line. (a,b)→ across the line.

Rotation: centre + angle + direction.

Translation: column vector x
y
(top = x, bottom = y).

Enlargement: centre + scale factor (incl. fractional & negative — Higher).

Invariant points: mirror line / centre of rotation / centre of enlargement.

Magnitude (H): |a| = √(x² + y²).

Arithmetic (H): add/subtract components; scalar × both parts; −a reversed.

Position vectors & proofs (H): AB = b − a; scalar multiple ⇒ parallel.

That's the whole of Edexcel 4MA1 Vectors & Transformation Geometry. Press Finish to see your score.

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