Problem 356. Square, Point inside, Triangles, Area
Level: High School, College, SAT Prep.
The figure shows a square ABCD of area
S. A point P is inside the square. If S1, S2,
S3, and S4, are the areas of triangles
PAB, PBC, PCD, and PAD, respectively, prove that S1 +
S3 = S2
+ S4 = S/2.