$\angle1\ and\ \angle8$  

 $\angle3\ and\ \angle7$  

 $\angle4\ and\ \angle5$  

 $\angle2\ and\ \angle5$  

 $\angle1\ and\ \angle8$  

 $\angle3\ and\ \angle7$  

 $\angle4\ and\ \angle5$  

 $\angle2\ and\ \angle5$  

 $\angle1\ and\ \angle8$  

 $\angle3\ and\ \angle7$  

 $\angle4\ and\ \angle5$  

 $\angle2\ and\ \angle5$  

 $180\degree$  

 $65\degree$  

 $115\degree$  

 $65\degree$  

 $180\degree$  

 $115\degree$  

 $131\degree$  

 $180\degree$  

 $49\degree$  

 $131\degree$  

 $180\degree$  

 $49\degree$  

Parallel lines have the same slope.

Parallel lines intersect at one point.

Perpendicular lines form a right angle.

 $\angle1\ and\ \angle2$  

 $\angle2\ and\ \angle6$  

 $\angle4\ and\ \angle8$  

 $\angle3\ and\ \angle7$  

 $\angle3\ and\ \angle2$  

 $\angle6\ and\ \angle8$  

 $\angle3\ and\ \angle6$  

 $\angle1\ and\ \angle9$