Parallel Lines
If two lines intersect, the pair of If AB is parallel to CD, then the co-
opposite angles are equal. interior angles are supplementary.
corresponding ∠ s; AB || CD Co-int ∠ s; AB || CD
B
B
𝑥
A 180° − 𝑥
D A
D
𝑥
𝑥
C
C
B
If AB is parallel to CD, then the
alternate angles are equal. 𝑥
A
alt ∠ s ; AB || CD D
𝑥
C
Vertically opposite angles are equal. The adjacent angles on a
straight line are supplementary.
Vert opp ∠s equal
∠s on a str line
𝑥
𝑥
180° − 𝑥
𝑥
If two lines intersect, the pair of If AB is parallel to CD, then the co-
opposite angles are equal. interior angles are supplementary.
corresponding ∠ s; AB || CD Co-int ∠ s; AB || CD
B
B
𝑥
A 180° − 𝑥
D A
D
𝑥
𝑥
C
C
B
If AB is parallel to CD, then the
alternate angles are equal. 𝑥
A
alt ∠ s ; AB || CD D
𝑥
C
Vertically opposite angles are equal. The adjacent angles on a
straight line are supplementary.
Vert opp ∠s equal
∠s on a str line
𝑥
𝑥
180° − 𝑥
𝑥
