Review: Angles & Equations

$$\angle1\ and\ \angle5$$  are corresponding angles.

$$\angle2\ and\ \angle7$$ are alternate interior angles.

$$\angle5\ and\ \angle8$$ are vertical angles.

$$\angle3\ and\ \angle7$$ are corresponding angles.

$$\angle1\ and\ \angle7$$ have a __________ relationship.

$$\angle3\ and\ \angle6$$ have a __________ relationship.

$$\angle2\ and\ \angle7$$ have a __________ relationship.

$$\angle1\ and\ \angle4$$ have a __________ relationship.

$$\angle3+\angle5=?$$  

(numbers only)

(a)  

Which equation represents the relationship between $$\angle2\ and\ \angle6$$  ?