I. The only problem involving an actual proof in the 13 sample problems for New York State's Fall, 2014 Common Core-based Regents Examination in Geometry:
II. One page of hundreds involving proofs in Weeks & Adkins A Course in Geometry (published in 1970):
III. Extra Credit:
These Weeks & Adkins problems appear only 1/6 of the way into the book, before the Corresponding Angles postulate, and therefore before the proof that the sum of the measures of the angles of an triangle is 180°.
With this in mind, contrast the level of difficulty of the early-in-the-course Weeks & Adkins proofs with the sample course-final New York State Regency Exam proof.