In this image, we are asked to identify the angle that forms a "same side interior angle" pair with angle 1.

In geometry, same side interior angles are pairs of angles located on the same side of a transversal line, and they lie between two parallel lines. These angles are supplementary when the lines are parallel, meaning their measures add up to 180°.

From the image:

• Angle 1 and angle 3 are on the same side of the transversal line that crosses the two parallel lines.
• They are both inside the parallel lines, making them a pair of same side interior angles.

Thus, the angle that is a same side interior angle with angle 1 is angle 3.

Would you like further explanation on this concept, or do you have any questions?

Here are five related questions for further exploration:

1. What are alternate interior angles, and how do they differ from same side interior angles?
2. How can you determine if two lines are parallel based on the properties of angles formed by a transversal?
3. What are corresponding angles, and where would they appear in this figure?
4. Can same side interior angles ever be congruent? Under what conditions would that occur?
5. How would you prove that angle 1 and angle 3 are supplementary in this setup?

Tip: Remember that same side interior angles are supplementary when lines are parallel, adding up to 180°.