Two boards, one four inches wide and the other six inches wide, are nailed together to form an X. The angle at which they cross is 60 degrees. If this structure is painted and the boards are separated what is the area of the unpainted region on the four-inch board? (The holes caused by the nails are negligible.) Express your answer in simplest radical form.

Here we have that the boards are crossing each other on their flat sides Therefore, when the boards are separated, the area of the unpainted region is the area of a parallelogram

The dimensions of the formed parallelogram are;

Interior angles = 60° and 120° (adjacent angles of a parallelogram)

Height, h of parallelogram formed = 4 inches

From the angle of crossing of the parallelogram, we have;

Angle between the width or perpendicular cross section of the 6 inches board and the angle of crossing of the two boards = 90° - 60° = 30°

Therefore, length of base, b of the parallelogram formed by the unpainted region is given as follows;

[tex]b = \frac{60}{cos(30)} = 40\cdot \sqrt{3} \ inches[/tex]

Therefore, the area of the parallelogram = b × h = 4 × 40·√3 = 160·√3 in.²

Hence, the area of the unpainted region on the four inch board = 160·√3 in.².