# what does this question about a matrix mean?

here is a question says :

what does that mean ?

I did my best to solve this question myself but i didn't find a way to solve it

is this question possible or there is something else that i don't understand it

the matrix is square ..

how it changes to singular?

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A singular matrix is a matrix which does not have an inverse. A matrix has an inverse if and only if its determinant is nonzero. Take the determinant and find the value(s) of $\alpha$ which makes the determinant zero. Then just take the $\alpha$ such that it means the condition of the problem - that is, $0 \leq \alpha <2\pi$.
but ! we know that a matrix of order " size " $n*n$ is called a square matrix .. and the above matrix is $2*2$ matrix .. so even if it has not an inverse it is still square ?? confusion ?? –  Maher May 19 '14 at 21:32