# How can I input matrix as the figure indicates

Please tell me how to input a matrix as drawn in the figure. Thanks for your help.

• At which point do you have a problem? Which is your code until now? You would like to have a solution to a specific issue, not us doing typing work, right? So perhaps show minimal starting code. – Stefan Kottwitz Mar 15 '15 at 11:52

I just find a solution for this problem as follows:

\begin{pmatrix}
1 &   &        &        &\alpha_{1k}    &          &    \\
& 1 &        &        &\alpha_{2k}    &          &    \\
&   &  \ddots&        & \vdots        &          &    \\
&   &        & \ddots &\alpha_{k-1,k} &          &    \\
&   &        &        &1              &          &    \\
&   &        &        &               &   \ddots &    \\
&   &        &        &               &          &   1
\end{pmatrix}


Do you have any idea or suggestion?

• Use \mathclap (from mathtools) for the α column, to improve horizontal spacing w.r.t. diagonal dots? – Bernard Mar 15 '15 at 12:31
• I make a try of mathclap command, but the columns get too close. While I get know of mathtools package. Thank you very much. – yangdawei Mar 15 '15 at 14:47