what is an alternate interior angle?

Answer 1

Z-angles. See the two angle in the Z.
Those two angles are equal.

Th

Answer 2

Alternate Interior Angle Theorem] If two lines cut by a transversal have a pair of congruent alternate interior angles, then the two lines are non-intersecting.

from your new friend:maryam

Answer 3

To help you understand this, draw 2 parallel lines on a piece of paper. Then draw another line which cuts across both parallel lines. The last line is called a transversal because it cuts across both the parallel lines. It may cut across the parallel lines at an angle, or it may also be perpendicular to both parallel lines.

Notice that there are 8 angles formed by the parallel lines and the transversal. 4 of them lie outside the parallel lines and 4 of them between or inside the parallel lines. Also, 4 of the angles are associated with each parallel line at the point where the transversal intersects it. Those angles which lie between the parallel lines are called interior angles, and those which lie outside are called exterior angles. Alternate interior angles are interior angles which lie on opposite sides of the transversal and whose vertices lie on the opposing parallel line. So, they not only alternate sides of the transversal, but they alternate the parallel lines with which they are associated. Alternate interior angles of parallel lines are always equal in measure and they are always supplemental to the angle which lies on the opposite side of the transversal from them (i.e. their sum is 180°). Also, there are always two pairs of alternate interior angles between any two parallel lines cut by a single transversal, with the measure of each member of one pair being the supplement of each member of the other, which follows logically from the preceding statement.

Answer 4

I need a diagram to show you this, so look at the link below.