UGC NET CSE | June 2019 | Part 2 | Question: 28

Question

Consider the following statements regarding $2D$ transforms in computer graphics:

$S1: \: \begin{bmatrix} 1 & 0 \\ 0 & -1 \end{bmatrix} $ is a $2 \times 2$ matrix that reflects (mirrors) only $2D$ point about the X-axis.

$S2:$ A $2 \times 2$ matrix which mirrors any $2D$ point about the $X$-axis, is a rotation matrix.

What can you say about the statements $S1$ and $S2$?

• A. Both $S1$ and $S2$ are true
• B. Only $S1$ is true
• C. Only $S2$ is true
• D. Both $S1$ and $S2$ are false

Answer 1

Answer is B: Only S1 is true.

Comments

reflecition is roaion by 180 degrees.

see  https://www.tutorialspoint.com/computer_graphics/2d_transformation.htm

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first matrix is reflection matrix about x-axis  S1 is true always 

 

S2 is 2x2 reflection matrix which is not same as  rotation  matrix  since  rotation matrix is   

and reflection matrix is 

1   0

0  -1   

for no value of theta  these 2 matrix can be same 

Ans should be 2