Let $A=\left[\begin{array}{ccc}b^2+c^2 & a^2 & a^2 \\ b^2 & c^2+a^2 & b^2 \\ c^2 & c^2 &…

Let $A=\left[\begin{array}{ccc}b^2+c^2 & a^2 & a^2 \\ b^2 & c^2+a^2 & b^2 \\ c^2 & c^2 & a^2+b^2\end{array}\right]$. If $a=\sin \frac{\pi}{6}, b=\cos \frac{\pi}{4}$ and $c=\cot \frac{\pi}{2}$, then $A$ is
  1. Symmetric matrix
  2. Skew-Symmetric matrix
  3. Singular matrix
  4. Non-singular matrix

Solution

$ \begin{aligned} & \text { Given, } a=\sin \frac{\pi}{6}=\frac{1}{2}, b=\cos \frac{\pi}{4}=\frac{1}{\sqrt{2}}, \\ & c=\cot \frac{\pi}{2}=0 \\ & \because \quad|A|=\left|\begin{array}{lll} \frac{1}{2} & \frac{1}{4} & \frac{1}{4} \\ \frac{1}{2} & \frac{1}{4} & \frac{1}{2} \\ 0 & 0 & \frac{3}{4} \end{array}\right| . \end{aligned} $ Here, $c_1=2 c_2$ $ \therefore \quad|A|=0 $ $\therefore A$ is singular matrix

Asked in: AP EAMCET 2022 (07 Jul Shift 2)

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