ABCD is a cyclic quadrilateral. Angle A, Angle B and Angle C form an arithmetic sequence in this order. What is Angle D in degrees?
I was pretty stuck on this question. Thanks!
Let A = A
Let B = A + d
Let C = A + 2d
Note that A + C will be supplementary......so....
A + (A + 2d) = 180
2A + 2d = 180 divide through by 2
A + d = 90
And B + D are also supplementary
(A + d ) + D = 180
90 + D = 180 subtract 90 from both sides
D = 90°
Note that B must also = 90°
And A , B , C are in arithmetic progression if A = 60° and C =120°