Find the best tutors and institutes for Class 12 Tuition
Q10(iii):
Express the following matrices as the sum of a symmetric and a skew symmetric matrix: (iii) $\begin{bmatrix} 3 & 3 & -1 \\ -2 & -2 & 1 \\ -4 & -5 & 2 \end{bmatrix}$
Solution :
Step 1: Theoretical Foundation
Any square matrix $A$ can be uniquely expressed as the sum of a symmetric matrix $P$ and a skew-symmetric matrix $Q$, defined as follows [Per the Theorem on Decomposition of Matrices]:
$A = P + Q$
Where:
- $P = \frac{1}{2}(A + A^T)$ [Symmetric matrix, as $P^T = P$]
- $Q = \frac{1}{2}(A - A^T)$ [Skew-symmetric matrix, as $Q^T = -Q$]
Step 2: Define Given Matrix and Transpose
Given $A = \begin{bmatrix} 3 & 3 & -1 \\ -2 & -2 & 1 \\ -4 & -5 & 2 \end{bmatrix}$
The transpose $A^T$ is obtained by interchanging rows and columns:
$A^T = \begin{bmatrix} 3 & -2 & -4 \\ 3 & -2 & -5 \\ -1 & 1 & 2 \end{bmatrix}$
Step 3: Calculate the Symmetric Matrix ($P$)
$P = \frac{1}{2}(A + A^T) = \frac{1}{2} \left( \begin{bmatrix} 3 & 3 & -1 \\ -2 & -2 & 1 \\ -4 & -5 & 2 \end{bmatrix} + \begin{bmatrix} 3 & -2 & -4 \\ 3 & -2 & -5 \\ -1 & 1 & 2 \end{bmatrix} \right)$
$P = \frac{1}{2} \begin{bmatrix} 6 & 1 & -5 \\ 1 & -4 & -4 \\ -5 & -4 & 4 \end{bmatrix} = \begin{bmatrix} 3 & 0.5 & -2.5 \\ 0.5 & -2 & -2 \\ -2.5 & -2 & 2 \end{bmatrix}$
Step 4: Calculate the Skew-Symmetric Matrix ($Q$)
$Q = \frac{1}{2}(A - A^T) = \frac{1}{2} \left( \begin{bmatrix} 3 & 3 & -1 \\ -2 & -2 & 1 \\ -4 & -5 & 2 \end{bmatrix} - \begin{bmatrix} 3 & -2 & -4 \\ 3 & -2 & -5 \\ -1 & 1 & 2 \end{bmatrix} \right)$
$Q = \frac{1}{2} \begin{bmatrix} 0 & 5 & 3 \\ -5 & 0 & 6 \\ -3 & -6 & 0 \end{bmatrix} = \begin{bmatrix} 0 & 2.5 & 1.5 \\ -2.5 & 0 & 3 \\ -1.5 & -3 & 0 \end{bmatrix}$
Step 5: Verification of Summation
To verify the decomposition, sum $P$ and $Q$:
$P + Q = \begin{bmatrix} 3 & 0.5 & -2.5 \\ 0.5 & -2 & -2 \\ -2.5 & -2 & 2 \end{bmatrix} + \begin{bmatrix} 0 & 2.5 & 1.5 \\ -2.5 & 0 & 3 \\ -1.5 & -3 & 0 \end{bmatrix} = \begin{bmatrix} 3 & 3 & -1 \\ -2 & -2 & 1 \\ -4 & -5 & 2 \end{bmatrix} = A$
Final Solution: The matrix is expressed as the sum of the symmetric matrix $\begin{bmatrix} 3 & 0.5 & -2.5 \\ 0.5 & -2 & -2 \\ -2.5 & -2 & 2 \end{bmatrix}$ and the skew-symmetric matrix $\begin{bmatrix} 0 & 2.5 & 1.5 \\ -2.5 & 0 & 3 \\ -1.5 & -3 & 0 \end{bmatrix}$.
More Questions from Class 12 Mathematics Matrices EXERCISE 3.3
- Q1(i): Find the transpose of each of the following matrices: (i) $\begin{bmatrix} 5 \\ \frac{1}{2} \\ -1 \end{bmatrix}$
- Q1(ii): Find the transpose of each of the following matrices: (ii) $\begin{bmatrix} 1 & -1 \\ 2 & 3 \end{bmatrix}$
- Q1(iii): Find the transpose of each of the following matrices: (iii) $\begin{bmatrix} -1 & 5 & 6 \\ \sqrt{3} & 5 & 6 \\ 2 & 3 & -1 \end{bmatrix}$
- Q2(i): If $A = \begin{bmatrix} -1 & 2 & 3 \\ 5 & 7 & 9 \\ -2 & 1 & 1 \end{bmatrix}$ and $B = \begin{bmatrix} -4 & 1 & -5 \\ 1 & 2 & 0 \\ 1 & 3 & 1 \end{bmatrix}$, then verify that (i) $(A + B)' = A' + B'$
- Q2(ii): If $A = \begin{bmatrix} -1 & 2 & 3 \\ 5 & 7 & 9 \\ -2 & 1 & 1 \end{bmatrix}$ and $B = \begin{bmatrix} -4 & 1 & -5 \\ 1 & 2 & 0 \\ 1 & 3 & 1 \end{bmatrix}$, then verify that (ii) $(A – B)' = A' – B'$
- Q3(i): If $A' = \begin{bmatrix} 3 & 4 \\ -1 & 2 \\ 0 & 1 \end{bmatrix}$ and $B = \begin{bmatrix} -1 & 2 & 1 \\ 1 & 2 & 3 \end{bmatrix}$, then verify that (i) $(A + B)' = A' + B'$
- Q3(ii): If $A' = \begin{bmatrix} 3 & 4 \\ -1 & 2 \\ 0 & 1 \end{bmatrix}$ and $B = \begin{bmatrix} -1 & 2 & 1 \\ 1 & 2 & 3 \end{bmatrix}$, then verify that (ii) $(A – B)' = A' – B'$
- Q4: If $A' = \begin{bmatrix} -2 & 3 \\ 1 & 2 \end{bmatrix}$ and $B = \begin{bmatrix} -1 & 0 \\ 1 & 2 \end{bmatrix}$, then find $(A + 2B)'$
- Q5(i): For the matrices A and B, verify that $(AB)' = B'A'$, where (i) $A = \begin{bmatrix} 1 \\ -4 \\ 3 \end{bmatrix}$, $B = \begin{bmatrix} -1 & 2 & 1 \end{bmatrix}$
- Q5(ii): For the matrices A and B, verify that $(AB)' = B'A'$, where (ii) $A = \begin{bmatrix} 0 \\ 1 \\ 2 \end{bmatrix}$, $B = \begin{bmatrix} 1 & 5 & 7 \end{bmatrix}$
- Q6(i): If (i) $A = \begin{bmatrix} \cos \alpha & \sin \alpha \\ -\sin \alpha & \cos \alpha \end{bmatrix}$, then verify that $A' A = I$
- Q6(ii): If (ii) $A = \begin{bmatrix} \sin \alpha & \cos \alpha \\ -\cos \alpha & \sin \alpha \end{bmatrix}$, then verify that $A' A = I$
- Q7(i): (i) Show that the matrix $A = \begin{bmatrix} 1 & -1 & 5 \\ -1 & 2 & 1 \\ 5 & 1 & 3 \end{bmatrix}$ is a symmetric matrix.
- Q7(ii): (ii) Show that the matrix $A = \begin{bmatrix} 0 & 1 & -1 \\ -1 & 0 & 1 \\ 1 & -1 & 0 \end{bmatrix}$ is a skew symmetric matrix.
- Q8(i): For the matrix $A = \begin{bmatrix} 1 & 5 \\ 6 & 7 \end{bmatrix}$, verify that (i) $(A + A')$ is a symmetric matrix
- Q8(ii): For the matrix $A = \begin{bmatrix} 1 & 5 \\ 6 & 7 \end{bmatrix}$, verify that (ii) $(A – A')$ is a skew symmetric matrix
- Q9: Find $\frac{1}{2}(A + A')$ and $\frac{1}{2}(A - A')$, when $A = \begin{bmatrix} 0 & a & b \\ -a & 0 & c \\ -b & -c & 0 \end{bmatrix}$
- Q10(i): Express the following matrices as the sum of a symmetric and a skew symmetric matrix: (i) $\begin{bmatrix} 3 & 5 \\ 1 & -1 \end{bmatrix}$
- Q10(ii): Express the following matrices as the sum of a symmetric and a skew symmetric matrix: (ii) $\begin{bmatrix} 6 & -2 & 2 \\ -2 & 3 & -1 \\ 2 & -1 & 3 \end{bmatrix}$
- Q10(iv): Express the following matrices as the sum of a symmetric and a skew symmetric matrix: (iv) $\begin{bmatrix} 1 & 5 \\ -1 & 2 \end{bmatrix}$
- Q11: If $A, B$ are symmetric matrices of same order, then $AB – BA$ is a
- Q12: If $A = \begin{bmatrix} \cos \alpha & -\sin \alpha \\ \sin \alpha & \cos \alpha \end{bmatrix}$, and $A + A' = I$, then the value of $\alpha$ is
CBSE Solutions for Class 12 Mathematics Matrices
Chapters in CBSE - Class 12 Mathematics
Top Tutors who teach Matrices
I,Mridula Das from Delhi ama professional Psychology teacher. I coach XI and XII grade CBSE students. I holds a Masters degree in Psychology and a B.Ed degree, and have also completed my MBA in Human Resources Management. Further ,I hold a PG Diploma in Guidance and Counselling. I have been teaching for the past 3 years in schools in West Delhi, and have guided 25-30 students per batch. According to my teaching style, I keep my class interactive and responsive and incorporate several visual aids in teaching. As a psychological expert, I understands student's minds set better and charters her teaching style accordingly. I teaches ,both online and offline classes as well.
Mridula ma'am is an excellent psychology teacher. What I loved most about her teaching style is that she always used really relatable and easy to understand examples to explain concepts, which made even the difficult topics feel simple. Her dedication and patience truly make her stand out as a teacher.I was able to score well, thanks to her guidance.
I have taught almost 5 years for 12 Tution
I am a mathematics teacher. I have been working in schools from last 6-7 years , and i was giving tutions at my home and even in an insitute in delhi from last 5-7 years. I shifted to tezpur,Assam in April 2021. my last job was in air force school hindan and I currently work at Air force school tezpur. i have a degree in msc mathematics and b.ed. i teach mathematics upto class 12. my key skills are in ms office , mathematics project, calligraphy , and can help out students in their various activities.
She is really amazing tutor you can ever have.She guides her students really well.She helps her students everytime. She motivates her students always. She supports her students always. She explains really nicely.
I am a teacher. I love teaching and want to share my knowledge with my students. I will take online classes. My approach combines clear concepts, regular practice, and student-friendly strategies to make learning effective and enjoyable.
"Found it to be a very intuitive learning methodology, practical approach, helpful in understanding."
I feel myself God-blessed, having been able to guide thousands of students/learners English, as a school subject as well as a language since 1992. I'm glad to notice that these learners have not only been doing well in their respective areas but also excelling in the real-life situations. May God bless them!!
My one-on-one tutoring experience in English and French was exceptional. The lessons were customized to my learning style and pace, which made a huge difference. My tutor was patient and skilled, offering clear explanations that helped me better understand grammar and improve my speaking abilities in both languages. The sessions were engaging, with interactive exercises and valuable feedback that kept me motivated. I've gained confidence in using English and French daily, and I highly recommend this personalized tutoring service!
Other Subjects in CBSE - Class 12
Download free CBSE - Class 12 Mathematics Matrices EXERCISE 3.3 worksheets
Download Now