A line segment has endpoints at (9 ,4 ) and (1 , 8 ). If the line segment is rotated about the origin by  pi /2 , translated horizontally by  5 , and reflected about the y-axis, what will the line segment's new endpoints be?

Jul 28, 2018

$\left(- 1 , 9\right) \text{ and } \left(3 , 1\right)$

Explanation:

$\text{Since there are 3 transformations to be performed label}$
$\text{the endpoints}$

$A = \left(9 , 4\right) \text{ and } B = \left(1 , 8\right)$

$\textcolor{b l u e}{\text{first transformation}}$

$\text{under a rotation about the origin of } \frac{\pi}{2}$

• " a point "(x,y)to(-y,x)

$A \left(9 , 4\right) \to A ' \left(- 4 , 9\right)$

$B \left(1 , 8\right) \to B ' \left(- 8 , 1\right)$

$\textcolor{b l u e}{\text{second transformation}}$

$\text{under a horizontal translation } \left(\begin{matrix}5 \\ 0\end{matrix}\right)$

• " a point "(x,y)to(x+5,y)

$A ' \left(- 4 , 9\right) \to A ' ' \left(1 , 9\right)$

$B ' \left(- 8 , 1\right) \to B ' ' \left(- 3 , 1\right)$

$\textcolor{b l u e}{\text{third transformation}}$

$\text{under a reflection in the y-axis}$

• " a point "(x,y)to(-x,y)

$A ' ' \left(1 , 9\right) \to A ' ' ' \left(- 1 , 9\right)$

$B ' ' \left(- 3 , 1\right) \to B ' ' ' \left(3 , 1\right)$

$\text{After all 3 transformations}$

$\left(9 , 4\right) \to \left(- 1 , 9\right) \text{ and } \left(1 , 8\right) \to \left(3 , 1\right)$