See How to Calculate the Area below, but first the calculator: The Calculator. Enter the radius, diameter, circumference or area of a Circle to find the other three. The calculations are done "live":

Cross sections are usually parallel to the base like above, but can be in any direction. Example: The vertical cross section through the center of this torus is two circles!

There are two main "slices" of a circle: A sector is like a slice of pizza, with a radius on two sides. A segment is the part of a circle cut off by a "chord" (a line connecting two points on the circle).

Example: a steel pipe has an outside diameter (OD) of 100mm and an inside diameter (ID) of 80mm, what is the area of the cross section? Convert diameter to radius for both outside and inside circles: R = 100 mm / 2 = 50 mm; r = 80 mm / 2 = 40 mm; Now calculate area:

Area Formula. How did we get that area formula? It is the area of the sector (the pie-slice region) minus the triangular piece. Area of Segment = Area of Sector − Area of Triangle. Looking at this diagram: With a bit of geometry we can work out that angle θ/2 = cos-1 (r − hr), so. Area of Sector = cos-1 (r − hr) r 2

Surface Area of a Cylinder. The Surface Area has these parts: Surface Area of Both Ends = 2 × π × r 2; Surface Area of Side = 2 × π × r × h; Which together make: Surface Area = 2 × π × r × (r+h)

Go to Surface Area or Volume. A torus is a fascinating 3D shape that looks like a donut or swim ring. It is created by revolving a smaller circle around a larger one.

This is a cross-section of a piece of celery. Cross sections make it easy to draw details of solid objects. In Geometry it is the shape made when a solid is cut through by a plane.

A cross section is the shape made by cutting straight across an object. The cross section of this object is a triangle..... it has the same cross section all along its length ..... so it's a triangular prism.

Here is a way to find the formula for the area of a circle: Cut a circle into equal sectors (12 in this example) Divide just one of the sectors into two equal parts. We now have thirteen sectors – number them 1 to 13: