The complement of $90°$ is $90°.$

Check whether the following indicated pairs of angles are adjacent :

Check whether the following indicated pairs of angles are adjacent :

Look at the figure given below and answer the following questions :

 Do $\angle \mathrm{AOB}$ and $\angle \mathrm{BOC}$ form a linear pair ?

Look at the figure given below and answer the following questions : 

 Are $\angle \mathrm{AOB}$ and $\angle \mathrm{COD}$ vertically opposite angles ?

Look at the figure given below and answer the following questions : 

 Do $\angle \mathrm{AOD}$ and $\angle \mathrm{DOC}$ form a linear pair ?