If the length of the diagonals of a parallelogram are equal, then which of these conditions is always true?
Find which of the following are not true:
1. All the sides of a rhombus are always equal in length.
2. All the sides of a parallelogram are always equal in length.
3. Diagonals of a parallelogram are equal in length.
4. Diagonals of a square are equal in length.
5. Diagonals of a rectangle are equal in length.
If the diagonals of a parallelogram are of equal lengths, the parallelogram is arectangle. Prove it.