Instruction

1

Single virtual place where arch will be installed, measure the height and width of the opening and determine the height of the arch. Typically, the height is 10% of the width of your door or interior of the opening.

2

Take a sheet of plywood or drywall, draw a line equal to the width of the opening, which let's call A and B. Note on the segment AB the middle, this will be point L. Swipe through the midpoint perpendicular. This perpendicular will coincide with your the Central axis of the opening (point C).

3

Connect the points A and C, and divide the resulting cut AC in half, receiving a Swipe through point D. point D another perpendicular to the intersection of it with the axis of the opening. Put there point.

4

Draw a arc of radius EA. Swipe between AB and the semicircle line exactly in the middle, calling it N. The drawing is ready.

5

The radius of the circle arches on the school formula: R = (L2 +H2) / 2H. Calculating the radius of the arch and knowing its height of rise (width of the Board), go to the calculation of the maximum possible length of the part that will have to be cut out from the width of the Board. Perform calculation according to the following formula: L= √2RH - H2

6

You should know that in order to make your arch items should be slightly larger than that obtained in the calculation, as they will have each other to be joined, imposing on each other. Before you cut directly arched design, it makes sense to make a template and try it, you will avoid errors and get the pattern ready for cutting your material - wood or drywall.

7

There is a simplified version of the calculation. Note above the door the height of the arch and add to the mark of 5-7 cm You will get the height of the arched opening. If the resulting height is greater than the height of the door, you have to peck. But to build the scheme of the arch so that all the angles and the circumference was equal to have all the same using formulas.

# Advice 2 : How to calculate arc length

The need to compute the length of arc may occur during different project works. Is the development of arched ceilings, the building of bridges and tunnels, laying of roads and Railways and much more. The initial conditions for the solution of this task can be very different. In order for the most optimal way to calculate the arc length, you need to know the radius of the circle and the Central angle.

You will need

- - a sheet of paper;
- a pair of compasses;
- - the range;
- - protractor;
- - a computer with AutoCAD;
- calculator.

Instruction

1

Construct a circle with a given radius. The principles of its construction in AutoCAD the same as on the sheet of paper. Having mastered the methods of constructing various geometric figures in the classical way, you will quickly understand how this is done on the computer. The difference is that in the ordinary construction with a compass you find the center of the circle at the point where you put the needle. In AutoCAD, look in the top menu click "arc" or "Arc". Choose build in the center, start point and angle and enter the desired parameters. Mark the center of the circle as O.

2

Using pencil and ruler or a computer mouse, swipe radius. If you draw on the sheet, then with a protractor lay aside a predetermined size of the angle. For this zero mark of the protractor will align with the dot On, check the desired angle and swipe through the resulting point of the second radius. Label the angle as α. You can call it as AOW, if appropriate letters to mark the points of intersection of the radii of the circle. You need to find the length of the arc AB.

3

If the size of the angle is specified in degrees, then arc length is equal to twice the product of the radius of the circle by a factor of π and the ratio of angle α to the full size of the Central angle of a circle. He is 360°. That is, it can be found by the formula L=2πRα/360°, where L is the desired arc length, R is the radius of the circle, and α is the size of an angle in degrees. The angle can be specified in radians. Then the arc length is equal to the product of the radius by the angle, i.e. L=RA. In this case, the rest of the formula has decreased in translating degrees to radian.

4

Designers often have to calculate the arc length, the value just estimated the height of the bridge or overlap and the span length. In this case, make a drawing. The span will be the chord and the height of the part radius. Swipe it from the top of the future arch is perpendicular to the chord and continue on to the intended center of the circle. The height divides the chord in half. The center will connect with the ends of the chord, thus obtaining a 2 radius. Calculate the radius by using the Pythagorean theorem, that is, R=√a2+(R-h)2.

5

Knowing the radius and the difference between him and the tall, by theorem of sines, find the magnitude of the half angle of the sector. Sine is the ratio of the opposite leg to the hypotenuse, i.e. sinα=a/R. In the table of sines to find the size of the angle and substitute it into the formula.

Note

The two points divide the circle into two arcs. The job can be specified, the length of which one need to find. In this case, you must calculate the greater angle, and subtracting from the full angle given is acute.