MathDB

5

Part of 1993 Turkey Team Selection Test

Problems(1)

Finding angle values such that quadrilateral is tangent

Source: Turkey IMO TST 1993 #5

7/7/2011
Points EE and CC are chosen on a semicircle with diameter ABAB and center OO such that OE⊥ABOE \perp AB and the intersection point DD of ACAC and OEOE is inside the semicircle. Find all values of ∠CAB\angle{CAB} for which the quadrilateral OBCDOBCD is tangent.
geometrytrigonometrygeometry unsolved