Please help me

[Chr1s]

The attached picture shows my problem.
i only have a basic level of math knowledge from school about 15yrs ago.

I need to build a number of ramps of various sizes and take off angles.

what I don't know is how to calculate the radius of the circle in order to mark these out properly without a bunch of trial and error.

I can give the height of it and the take off angle but nothing more.

the side marked A is of little consequence but I guess you'll work that out in the course of solving the problem.

ultimately I need an equation where I can enter the angle and height, which gives me the radius.

Im sure its less complicated than I think and your help will be greatly appreciated.

Thanks

 

[JeffM]

The attached picture shows my problem.
i only have a basic level of math knowledge from school about 15yrs ago.

I need to build a number of ramps of various sizes and take off angles.

what I don't know is how to calculate the radius of the circle in order to mark these out properly without a bunch of trial and error.

I can give the height of it and the take off angle but nothing more.

the side marked A is of little consequence but I guess you'll work that out in the course of solving the problem.

ultimately I need an equation where I can enter the angle and height, which gives me the radius.

Im sure its less complicated than I think and your help will be greatly appreciated.

Thanks

I am having trouble figuring what the circle and the triangle in your drawing have to do with each other. I am sure it is obvious to you, but if it has to do with building physical things, I am an utter klutz. If I am following you, you have a length (presumably the number of feet you want the ramp to rise vertically and the angle at which you want it to rise, and want to find the other two lengths relevant to the ramp, namely the horizontal length from start to finish and the length of the ramp itself. Is that it?

If I am anywhere close to figuring out what your problem is, it can be solved by very simple trigonometry. You will need to get a scientific calculator (there is one available as a free app within Windows 7; look for "Calculator" under "Accessories," and under the "View" tab, select "Scientific"). You may have an option to use "degrees" or "radians"; select "degrees." Mathematicians find measuring angles in radians convenient, but degrees are standard in day-to-day work.

In general, for any right triangle, you can use the trigonometric functions to figure out the length of all three sides from the length of one side and the measure of either angle not including the 90 degree one.

A "trigon" is just another word for a triangle, and "metry" comes from the Greek word for measuring. The whole subject was originally developed for just this sort of problem. It will take you three minutes to learn the basics (if, that is, I understand what you are asking).

 

[Bob Brown MSEE]

use sin

Let h=height
Let a=angle
Let r=radius

sin(a)=(r-h)/r


Example: a=35 deg, h=6ft

sin(a)=(r-h)/r
0.57=(1-h/r)
0.43=h/r
r=6/0.43 ft
r=14 ft

 

[Chr1s]

Bob, that's exactly what I'm after.

Thanks very much for your help.