Question

ABCD is a quadrilateral with angleA=angleC and angleB=angleD.If angleA is twice angleB, find the measure of each angle

Answer 1

Let b be x
than a = c = 2x
and b = d = x
so by angle sum property we have
a + b + c + d = 360°
or
2x + x + 2x + x = 360°
6x = 360°
x = 360÷ 6
x = 60°
2x = 60°×2 = 120°
since b is x we have
b = d = x = 60°
and a = c = 2x = 120°
So your answer is
A = 120°
B = 60°
C = 120°
D = 60°