Answer:
Then you don't change the sign.
Two like signs become a positive sign.
Two unlike signs become a negative sign.
Step-by-step explanation:
x = 60°
AOB Center: O AB: diameter
arc ADB = 180°
arc DB = 180 - arc AD = 80°
x = 1/2 x ( arc DB + arc AC) = 1/2 x (80 + 40) = 60°
