1, geometric features: the side and diagonal faces are triangles; The section parallel to the bottom surface is similar to the bottom surface, and its similarity ratio is equal to the square of the ratio of the distance from the vertex to the section to the height.

2. Definition of a cone: A right-angled side of a right-angled triangle is used as the rotation axis to rotate a Zhou Suocheng.

3. The front view reflects the height and length of the object; The top view reflects the length and width of the object; The side view reflects the height and width of the object.

4. When the slope of the straight line is 0, k=0 and the equation of the straight line is y=y 1.

5. When judging the parallelism and verticality of a straight line by slope, we should pay attention to the existence of slope.