I wish you good grades in the senior high school entrance examination ~ ~ ~
Outline of a circle
4. Bow area 1) S bow =S sector -S δ OAB
2) S bow =S fan +S δ OAB
Second, the lateral area of the cone and the total area 1 The figure obtained by rotating the rectangular ABCD around the straight line AB is called a cylinder. The straight line AB of the rotation axis is called its axis.
The length of the AB side of a rectangle on the AB axis is called its height. The curved surface formed by the rotation of the side DC parallel to the axis is called its side. No matter where it rotates, this side is called the generatrix of the cylinder.
The circular surface formed by the rotation of the sides ad and BC perpendicular to the axis is called its bottom surface.
4, the cone is surrounded by a bottom and a side, we put the cone.
The connecting line between any point on the circumference of the bottom surface and the vertex of the cone is called a cone.
The line segment connecting the vertex and the bottom center is called the height of the cone.
The side of the cone is unfolded along the generatrix of the cone, and a sector with arc length equal to the circumference of the bottom of the cone and radius equal to the length of the generatrix of the cone is obtained.
The lateral area of a cone is the long fan-shaped area of a bus, the arc length of the bus is the perimeter of its bottom surface, the radius is a cone, and the total area of the cone is the sum of its lateral area and its bottom area.
5. Let the bottom radius be R and the bus length be L, then
S side = l 2 π r = π rl
S all =πrl+πr
Quantitative relationship: external: d>R+r+r? Four common tangents
Circumscribed: d=R+r? Three common tangents
Intersection: r-r < d < r+r? Two common tangents
Inner cut: d=R-r? common tangent
Include: d