# Sign, sin, sine

Geometry Level 4

In parallelogram $$ABCD$$, angles $$B$$ and $$D$$ are acute while angles $$A$$ and $$C$$ are obtuse. The perpendicular from $$C$$ to $$AB$$ and the perpendicular from $$A$$ to $$BC$$ intersect at a point $$P$$ inside the parallelogram. If $$P B = 700$$ while $$P D = 821$$, what is $$AC$$?

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