Answer:
BC = 100°
Step-by-step explanation:
The chord- chord angle BDC is half the sum of the arcs intercepted by the angle and its vertical angle, that is
[tex]\frac{1}{2}[/tex] ( BC + AE) = 85° ( multiply both sides by 2 to clear the fraction )
BC + AE = 170°
BC + 70° = 170° ( subtract 70° from both sides )
BC = 100°
