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Printimc
geometry intermediate
Problem
Quadrilateral has , and . What is the degree measure of ?
(A)
(B)
(C)
(D)
Solution
* Note: This solution requires the use of cyclic quadrilateral properties but could be a bit time-consuming during the contest. To start off, draw a diagram like in solution two and label the points. Create lines and . We can call their intersection point . Note that triangle is an isosceles triangle so angles and are each degrees. Since equals , angle equals degrees, thus making angle equal to degrees. We can also find out that angle equals degrees. Extend and and let their intersection be . Since angle plus angle equals degrees, quadrilateral is a cyclic quadrilateral. Next, draw a line from point to point . Since angle and angle point to the same arc, angle is equal to degrees. Since is an isosceles triangle (based on angle properties) and is also an isosceles triangle, we can find that is also an isosceles triangle. Thus, each of the other angles is degrees. Finally, we have angle equals degrees.
Final answer
C