Practicing Success
AB is a chord in a circle with centre O. AB is produced to C such that BC is equal to the radius of the circle. C is joined to O and produced to meet the circle at D. If ∠ACD = 32°, then the measure of ∠AOD is ______. |
48° 96° 108° 80° |
96° |
In \(\Delta \)OBC If OB = BC, then \(\angle\)BOC = \(\angle\)BCO = \({32}^\circ\) As we know, \(\angle\)OBA = \(\angle\)BOC + \(\angle\)BCO = 32 + 32 = 64 If OA = OB, then \(\angle\)OBA = \(\angle\)OAB = 64 In\(\Delta \)AOB \(\angle\)AOB + \(\angle\)OAB + \(\angle\)OBA = 180 \(\angle\)AOB + 64 + 64 = 180 \(\angle\)AOB = 180 - 128 = 52 \(\angle\)AOD + \(\angle\)AOB + \(\angle\)BOC = 180 \(\angle\)AOD + 52 + 32 = 180 \(\angle\)AOD = 180 - 84 = \({96}^\circ\). |