To determine the measure of angle 3 given that angle 1 is 63°, we can analyze the relationship between the angles created by the intersection of the two lines.
Angle 1 and angle 3 are opposite each other at the point of intersection. Angles that are opposite each other when two lines intersect are called vertical angles. Vertical angles are always equal in measure.
Since angle 1 is 63°, angle 3 must also be 63° because they are vertical angles.
Therefore, the correct response is: Angle 3 is 63° because angle 1 and angle 3 are vertical angles.