1. Cubic multiplication refers to making a cube with a ruler and gauge to make its volume twice that of a known cube.
2. bisecting any angle means bisecting any angle with a ruler method.
3. Turning a circle into a square means making a square with a ruler method, and its area is equal to that of a known circle.
4. The proof of Goldbach conjecture is the proof of even number and prime number correlation theorem. If this theorem is proved, Goldbach's conjecture can be proved.