If the cosine of each angle A, B, C, and D is -1/2, which of the following can be concluded? (See attached drawing)

(A) Points A, E and D are collinear
(B) cos angle E = 1/2
(C) -AED is a right angle
(D) -AED and -EDC are complementary
(E) the given information is self-contradictory

Question

If the cosine of each angle A, B, C, and D is -1/2, which of the following can be concluded? (See attached drawing)

(A) Points A, E and D are collinear
(B) cos angle E = 1/2
(C) -AED is a right angle
(D) -AED and -EDC are complementary
(E) the given information is self-contradictory

anonymous · Answer

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anonymous · Answer

If the cosine of each of those 4 angles is -1/2, then each of those interior angles must be 60 degrees.  Also consider that all of the angles of a pentagon add up to 540 degrees.  That should get you started.