Wrong signs in translation vectors
"The Vector Sign Slip"
The Mistake in Action
Shape A is translated to shape B. A moves 3 left and 2 up.
Wrong: Vector = $\begin{pmatrix} 3 \\ 2 \end{pmatrix}$
Why It Happens
Students forget that left and down are negative directions. They write the numbers without considering direction.
The Fix
In a translation vector $\begin{pmatrix} a \\ b \end{pmatrix}$:
Horizontal (top number):
- Right = positive
- Left = negative
Vertical (bottom number):
- Up = positive
- Down = negative
3 left and 2 up = $\begin{pmatrix} -3 \\ 2 \end{pmatrix}$
Check: Trace a point — does it end up in the right place?
Spot the Mistake
Can you identify where this student went wrong?
A moves 3 left and 2 up
Vector = $\begin{pmatrix} 3 \\ 2 \end{pmatrix}$
Click on the line that contains the error.
Related Topics
Learn more about the underlying maths: