While I agree about proofs it's not intuitive to me. A triangle can clearly be visualized as half a square. Look at any videogame square made of 2 polygons. A

While I agree about proofs it's not intuitive to me. A triangle can clearly be visualized as half a square. Look at any videogame square made of 2 polygons. A 2D projection of a cone isn't intuitively 1/3 of a cylinder with the same dimensions.