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Solve the Triangle

Source: 1993 National High School Mathematics League, Exam One, Problem 5

February 27, 2020

Problem Statement

In ABC\triangle ABC, cac-a is equal to height on side ACAC. Then, the value of sinCA2+cosC+A2\sin\frac{C-A}{2}+\cos\frac{C+A}{2} is (A)1(B)12(C)13(D)1\text{(A)}1\qquad\text{(B)}\frac{1}{2}\qquad\text{(C)}\frac{1}{3}\qquad\text{(D)}-1