Given : ∠ABC=75°andAD∥BC To find : ∠BCD=? Solution : In a cyclic quadrilateral, sum of opposite angles is supplementary. ⇒ ∠ABC+∠ADC=180° ⇒ ∠ADC = 180°− 75°= 105° Also, ∠ADC + ∠BCD = 180° [Angles on the same side of transversal] ⇒ ∠BCD = 180° − 105° = 75°