The measure of the angle between intersecting chords is equal to the mean of the measures of their intercepted arcs. Since <AED and <BEC are vertical angles, (mAD + mBC)/2 = 42. Then mBC = (42)(2) - 58 = 26
I am really lost with this. i need major help!!!! It says that <AED and <BEC are verticle making <BEC measure also 42. So with that in mind how did they come to the conclusion that arc BC is twenty-six?