Advice 1: How to calculate the cross-sectional area

When solving problems in geometry is necessary to calculate the areas and volumes of shapes. If you make any shape cross section, having information on the parameters of the figure itself, you can find the area of this section. You need to know the special formulas and have spatial thinking. You will need
• Ruler, pencil, eraser.
Instruction
1
Ball is a special case of the simplest three-dimensional figure. Through it, you can spend an infinite amount of sections, and any of them would be around. This happens regardless of how close the section is to the center of the ball. To calculate the area of the resulting cross-section is the easiest in that case, if it is carried out through the center of a ball whose radius is known. In this case, the area of the cross section is equal to:S=NR^2.
2
The other figure, the area of the cross section which you want to find in geometry problems is a parallelepiped. It has edges, and faces. Face is one of the planes of a parallelepiped (cube), and rib - side. The parallelepiped whose edges and faces are equal is called a cube. All sections of the cube squares. Knowing this property, calculate the area of cross-section-square:S=a^2, where a is the edge of the cube and the side section.
3
If the conditions of the problem given a regular parallelepiped, in which all faces are different, the cross section can be a square and a rectangle with different sides. The cross section drawn parallel to the two square faces is a square, and the cross section drawn parallel to two rectangular - rectangle. If the section passes through the diagonal of the parallelepiped, it is also a rectangle.
4
The area of the square cross-section parallelepiped can be found using the same formula as for a cross-section of the cube. If the cross section of the parallelepiped is a rectangle, find it, knowing two parameters, the length and width of the two rectangular faces:S=a*b, where a is the edge length, b -width of the verge.Diagonal cross section of a parallelepiped find by multiplying the diagonal of the bottom base to the height of the parallelepiped:S=d*h where d is the diagonal of the base, h is the height of the base.
5
Cone - one of the figures of rotation, the cross section of which can have different form. If you cut the cone parallel to the lower base section is a circle and if we draw a parallel section in half through the top of the cone, you get a triangle. In other cases, sectionmi will be a trapezoidal shape.If the cross section is a circle, calculate its area according to the following formula:S=NR^2.Square cross-section, which is a triangle is equal to the product of half the base to the height:S=1/2f*h , where f is the base of the triangle, h is the height of the triangle.

Advice 2 : Nuances in calculating the length of cable for wiring

You need to purchase material for electrical installation. If the work is done by professionals, they calculate and announce the full list and the required amount of materials. But if you decided to take matters into your own hands, you just need to know a few simple rules when calculating the required cable length. Instruction
1
The most important thing in the calculation is to determine how you will carry out the installation and connection of wiring. There are two options: with camshaft. without boxes and switchgear. boxes (wire connections produced in podrozetnika).
2
Also, you should choose the method of laying cable on the floor, on the ceiling or on the walls (near the ceiling or above the floor). It is worth noting that it is better to choose one option and if there is no particular need to combine them. If you are not sure that you will be able everywhere to lay cable in the same way, it is better visually to calculate the whole route.
3
In the measurement of each segment note and add the length required to raskrucheny 15-20 cm to the food. boxes and podrozetnika and 30-40 cm in the shield (depending on the size of the shield length may be more, I think conventional, the housing shield 12 modules).
4
It is worth considering that, if you plan to install several outlets on the same wall, you can connect them with ribbon cable, that is, the power to lead in the near the other plug from her. This is the option to count separately, given the anticipated load on a particular socket.
5
And the last rule at the end of the calculations, the amount of increase in a big way, well, or add a few meters to spare. If you want some more rostochek, and their is never enough.