1. Find the length of a side of a square if the radius is 10.
2. Find the length of an apothem of a square if the perimeter is 40.
3. In an equilateral triangle find the length of a radius if the length of a side is 12.
4. What is the length of the longer diagonal of a rhombus if its area is 16 and the length of one of the diagonals is 8.