Ok so lets first determine all the angles of the triangle.
Given:
Angle A = 90
Angle B = 45
Angle C = ?
If we add up all the angles of any triangle, we should get 180 degrees.
Therefore, Angle C = 90 (angle A) - 45 (angle B) = 45 degrees.
Since there was a ray drawn from A through C the exterior angle of angle C is angle 1.
Any straight line should equal to 180 degrees.
Therefore, angle 1 = 180 - angle C = 135
Answer: angle 1 = 135 degrees
