Given: OB bisects ∠ABC OC bisects ∠BCD To find: the measure of ∠BOC [Note: if you had proved that OB and OC intersect at the center, you could just observe that ∠BOC is a central angle and has measure. But we will assume you haven't proved that.] The sum of the measures of the interior angles of an n-sided polygon is given by the formula (n-2)×180° Since this is a heptagon, n=7 and the sum of the measures of the interior angles is (7-2)×180° = (5)×180° = 900° Since this heptagon is regular, all the interior angles are congruent and have equal measure. Therefore m∠ABC = m∠BCD = Since OB and OC bisect those interior angles, m∠OBC = m∠OCB = × = Since the sum of the measures of the interior angles of ᐃBOC is 180°, m∠OBC + m∠OCB + m∠BOC = 180° + + m∠BOC = 180° + m∠BOC = 180° m∠BOC = 180° - m∠BOC = - m∠BOC = = ° Edwin