Prove Lines Parallel
1. Find the value of $x$ that makes $m \parallel n$.
**a.** Given angles: $100^\circ$ and $2x^\circ$ are corresponding angles.
Since $m \parallel n$, corresponding angles are equal:
$$100 = 2x$$
Solve for $x$:
$$x = \frac{100}{2} = 50$$
**b.** Given angles: $(5x + 23)^\circ$ and $(7x + 13)^\circ$ are alternate interior angles.
Since $m \parallel n$, alternate interior angles are equal:
$$5x + 23 = 7x + 13$$
Solve for $x$:
$$23 - 13 = 7x - 5x$$
$$10 = 2x$$
$$x = 5$$
2. Draw two parallel lines and a transversal cutting through at $35^\circ$.
- Corresponding angles are equal to $35^\circ$.
- Alternate interior angles are also $35^\circ$.
- Consecutive interior angles are supplementary, so $180 - 35 = 145^\circ$.
Label all angles accordingly:
- Angles corresponding to $35^\circ$ are $35^\circ$.
- Angles supplementary to $35^\circ$ are $145^\circ$.
3. Proof that $p \parallel r$ given $g \parallel h$ and $\angle 1 \cong \angle 2$.
**Given:** $g \parallel h$, $\angle 1 \cong \angle 2$
**To Prove:** $p \parallel r$
**Proof (Two-column):**
| Statements | Reasons |
|---|---|
| 1. $g \parallel h$ | Given |
| 2. $\angle 1 \cong \angle 2$ | Given |
| 3. $\angle 1$ and $\angle 3$ are alternate interior angles formed by transversal $g$ with lines $p$ and $r$ | Definition of alternate interior angles |
| 4. $\angle 2$ and $\angle 3$ are corresponding angles | Angle relationships in the diagram |
| 5. $\angle 1 \cong \angle 2$ implies $\angle 3$ is congruent to $\angle 1$ and $\angle 2$ | Transitive property of congruence |
| 6. Since $\angle 1 \cong \angle 3$, lines $p$ and $r$ are parallel | Converse of alternate interior angles theorem |
Thus, $p \parallel r$ is proven.