Answer:
180 degrees
Step-by-step explanation:
Lets call the unknown Angle next to angle C "ANGLE D"
1. Your given the angle 45 degrees.
2. (45 degree angle) can correspond to Angle D,
because of the alternate exterior angles definition- two lines (angles) that are on diagonal opposite sides of one another outside of the two parallel lines.
3: (45 degree angle) is an alternate exterior angle to its corresponding diagonal angle Angle D, this can also be said for (Angle C) and (angle B).
4: Now that the angles are known- (Angle C) is an alternate exterior angle to (Angle B). (45 degree angle) is an alternate exterior angle to Angle D
We can now use
The alternate Exterior angles Theorem- If two parallel lines are intersected by a transversal, then the alternate exterior angles are congruent.
4: we now know that (45 degree angle) is congruent to Angle D. And (angle C) is congruent to (angle B).
-Angle D and (45 Degree angle) are both 45 degrees since they are both alternate exterior angles to one another. And (Angle C) and (Angle B) have the same angle measure because they are alternate exterior angles to one another.
5: take a look at (angle C) and Angle D notice the transversal- (line that intersects two parallel lines), and how it creates a linear pair. Notice that the transversal has created the angles of (angle B) and (45 degree angle) to be linear pairs as well.
- Linear Pair definition- If two adjacent lines have rays pointing in opposite directions they are linear pairs.
Also the definition of a Linear Pair identifies as Supplementary. Supplementary is an angle that has a total of 180 degrees.
6: If (45 degree angle) and Angle B make a linear pair, and linear pairs have a total of 180 degrees, then solve for the angle measure of (angle B)
180= 45 + measure of (angle B)
180-45= 135
135 = measure of (angle B)
45 + 135= 180 degrees
7: The measure of (Angle B) is 135 degrees and since (Angle B) is congruent to (Angle C), the measure of (Angle C) is 135 degrees.
Therefore, (45 degree angle) and (Angle B) are 180 degrees total and (Angle C) and (Angle D) are 180 degrees total.
Now, that all exterior angle measures are found, it can be concluded that Angle A) is the same as the total measure of its exterior angle, since it is the same line that makes up the linear pair.
Therefore, (Angle a) is 180 degrees.
