abcd is a quadrilateral calculate the value of x

ABCD is a quadrilateral. What is the value of cos 1/2 (A + C) + cos 1/2 (B + D)?

1. 0
2. 1
3. sin 1/2  (B + D)
4. cos 1/2 (B + D)

Answer

Option 1 : 0

abcd is a quadrilateral calculate the value of x