Quadrilateral CDEF is inscribed in circle A. Which statements complete the proof to show that ∠CFE and ∠CDE are supplementary? Quadrilateral CDEF is inscribed in circle A. Quadrilateral CDEF is inscribed in circle A, so m arc CDE+ m arc CFE= 360°. ∠CFE and ∠CDE are , which means that their measures are one half the measure of their intercepted arcs. So, m arc CDE= 2 ⋅ m∠CFE and arc CFE= 2 ⋅ m∠CDE. Using the , 2 ⋅ m∠CFE + 2 ⋅ m∠CDE = 360°. Using the division property of equality, divide both sides of the equation by 2, resulting in m∠CFE + m∠CDE = 180°. Therefore, ∠CFE and ∠CDE are supplementary. inscribed angles; substitution property of equality central angles; substitution property of equality inscribed angles; addition property of equality central angles; addition property of equality