Question

PLEASE HELP!!

Answer 1

Answer:

D.130°

Step-by-step explanation:

An arc measure ia an angle an arc makes with the circle's centre and is proportional to the angle it subtends to the circumference, arc length.

-Given that  AC and BC are diameters, then $\angle AOB =\angle DOC$ since they are alternate angles.

$\angle AOB =\angle dOC=180\textdegree\\\\3x-70=x+10\\\\x=40\textdegree$

#Since angles on one side of a diameter sum up to 180°, mBC is calculated as:

$(3x-70)+m\angle BC=180\\\\M\angle BC=180+70-3\times 40\\\\=130\textdegree$

Hence, mBC=130°