We define the crossing number of a knot $$K$$ to be the minimal number of crossings in any diagram of $$K$$. Surely we can easy prove that there do not exist knots with crossing number $$1$$ and $$2$$ (because suppose well, then such knots are equivalent with the unknot, thus contradiction). But I want to prove now that the only knots with crossing number $$3$$ are the two trefoils knots. Surely both are inside the set of knots with crossing number 3, but the other site?! Or is this just trying?? Look up also to a torus link $$T_{p,q}$$. I want to prove this statement: $$T_{p,q}$$ is a knot (thus not a link) if and only if $$p$$ and $$q$$ are coprime. Can someone help me?
Hint 2: Recall that the definition of a torus knot is the image of a closed curve on the surface under a smooth embedding of the torus into $\mathbb{R}^3$. If we regard the torus as $\mathbb{R}^2/\mathbb{Z}^2$, all closed curves are homotopic to the image of a straight lines under identification. The coefficients $p,q$ are related to the slope of the line. Can you relate $p$ and $q$ to the number of components of the image of the line?