ABC is a triangle inscribed in a semicircle of diameter AB. What is \cos(A+B) + \sin(A+B) equal to?

  1. A. 0
  2. B. \frac{1}{4}
  3. C. \frac{1}{2}
  4. D. 1

Correct Answer: D. 1

Explanation

The angle subtended by a diameter at the circumference is always a right angle, so \angle C = 90^\circ. By angle sum property, A + B = 90^\circ. Therefore, \cos(90^\circ) + \sin(90^\circ) = 0 + 1 = 1.

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