| A | B |
|---|
| rectangle | a=bh where b=base, h=height |
| parallelogram | a=bh where b=base, h=heighth (be careful not to use length of side) |
| triangle | 1/2bh where b=base, he=height |
| trapezoid | 1/2(B1+B2)h where B1= base1, B2=base2 and h=height |
| area of a regular polygon with n sides | 1/2asn where a=apothem (a segment from the center of the polygon to a side of the polygon -not an angle) s= side n= number of sides in polygon |
| circle | pi r^2 (reads pi r squared) where pi=3.14, r= radius |
| sector (looks like a pie slice) | a/360 x pi x r^2 (reads a degrees divided by 360 degrees multiplied by 3.14 multiplied by the radius squared) |
| segment (looks like a pie slice less a triangular chunk) | a/360 x pi x r^2 - 1/2 bh (notice this is the formula of the area of a sector minus the area of a triangle) |
| annulus (an annulus is a large circle with a smaller circle removed from it) | pi x R^2 - pi xr^2 (reads pi or 3.14 multiplied by Radius of large circle squared - pi multiplied by radius of smaller- inner circle squared---notice this is just finding the area of both circles then subtracting the smaller circle's area from the larger circle's area) |
| kite | 1/2(D1D2) (reads 1/2 multiplied by length of diagonal 1 multiplied by the length of diagonal 2 |
| surface area of a prism (rectangular box) | 2bh + 2 bd + 2 hd (where b= base, h= height and d= depth--this gives you a 3-D box--formula reads two times base time height plus two times base times depth + two times heighth times depth---you're adding up the areas of the 2 sides that make the top and bottom of the box with the area of the 2 sides that make the front and back added to the area of the 2 panels that form the sides.) |
| surface area of a square-based pyramid | 4 x 1/2b(l) + b^2 (where b = base length and l= slant height--what's a pyramid but 4 equal triangles leaning up against each other on top of a base--so notice the formula has you taking the area of one triangle then multipliying it by four to get the total area of all the triangles then adding it to the area of the flat square base) |
| surface area of a cylinder | 2pi x r^2 = 2pi x r x h (where r=radius, h=height or length of cylinder this is NOT the diameter of the cylinder!!--formula reads 2 times pi times the radius squared + 2 times pi times the radius times the height or length of the cylinder) Notice you're finding the area of the circles that make the top and bottom of the cylinder and adding these to the lateral surface of the cylinder. |
| surface area of a right cone | pi x r x l + pi r^2 ( where r=radis, l= slant height--formula reads pi times radis times slant height + pi times radius squared --here you've added the lateral surface area of the cone to the circular area of the base) |
