Five Squares on a Rhombus

Strategies and Hints

  1. From the Pythagorean Theorem, the diagonal of a 6-by-6 square is . Half this length is .

  2. The key triangle is shaded in the drawing below.

  3. Since the two short sides of the shaded triangle are known, and its obtuse angle is 120° (45° + 30° + 45°), the Law of Cosines can be used to find the length of the third side.

Solution

The shaded triangle is the key to the solution.

Each short side equals . Using the Law of Cosines with an angle of 120°, the long side of the triangle is . So, the area of the square is 54 square units.