Question : Three consecutive angles of a cyclic quadrilateral are in the ratio of 1 : 4 : 5. The measure of the fourth angle is:
Option 1: 120°
Option 2: 60°
Option 3: 30°
Option 4: 80°
Correct Answer: 60°
Solution :
Given: Three consecutive angles of a cyclic quadrilateral are in the ratio of 1 : 4 : 5.
We know that the sum of the opposite angles of a cyclic quadrilateral is 180°.
Let
Since
So,
⇒
⇒
Since
So,
⇒
⇒
⇒
⇒
So, the measure of the fourth angle is 60°.
Hence, the correct answer is 60°.
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