Answer:
7. Always
8. Always
9. Always
10. Always
Explanation:
7. Corresponding angles theorem states if two parallel lines are cut by a transversal, then the pairs of corresponding angles are congruent.
Thus, corresponding angles are always congruent.
8. Vertical angles theorem states that vertical angles, angles that are opposite each other and formed by two intersecting straight lines, are congruent.
Thus, vertical angles are always congruent.
9. Same-side interior angles theorem states that when two lines that are parallel are intersected by a transversal line, the same-side interior angles that are formed are supplementary, or add up to 180 degrees.
Thus, same-side interior angles are always congruent.
10. Two angles are said to be linear if they are adjacent angles formed by two intersecting lines. The measure of a straight angle is 180 degrees, so a linear pair of angles must add up to 180 degrees. Hence, a linear pair of angles are always supplementary