In the given figure, sides AB and AD of quad. ABCD are produced to E and F respectively. If ∠CBE=100∘ then ∠CDF=?
(a) 100∘
(b) 80∘
(c) 130∘
(d) 90∘
ANSWER:
( b ) 80°
In a cyclic quadrilateral ABCD, we have:
Interior opposite angle, ∠ADC= exterior ∠CBE = 100°
∴ ∠CDF = (180° - ∠ADC) = (180° - 100°) = 80° (Linear pair)