Math/Sundial help please!

[SlayerZ99]

I need to make and describe the process of making an accurate sundial

http://plus.maths.org/content/brown townemmatic-sundials-how-build-one-and-why-they-work

I've already made the sundial but Im confused

if you scroll down to Why does an brown townemmatic sundial work? I dont understand what is going on when they are talking about the R radius of the circle on which the sun moves

can someone help me understand this?

[Ad Bot]

[SlayerZ99]

Ok I understand what they are saying but how am I supposed to know the R radius that the circle of the sun makes?

If I dont know that I cant figure out the azimuth

[Doomonkey]

I don't think you need the radius.



EDIT: Essentially, you have x and y which are both functions of R, but you are dividing them so the radius ceases to become a factor.

[SlayerZ99]

I don't think you need the radius.



EDIT: Essentially, you have x and y which are both functions of R, but you are dividing them so the radius ceases to become a factor.

But in order to find x and y wouldnt I need the radius?


After reading over again I dont think its necessary to have this, I think this is if you want the pointer to touch the ellipse at all times

then again this sections is very confusing for me

[Markey]

ogma big kid math!11!1!!1one

[SlayerZ99]

Ok for the radius I put in the radius of the short N-S side of my ellipse which happened to be 2.7 in
I plugged those in and got x = .70 in y= 1.76
If I take those and put that in z = 1/tan(1.76/.7) i get 22.8 degrees
This is spot on for the degrees from the y-axis of my 1 pm hour mark.

But I still dont get this

"During the day, z changes and by finding z we can find the time. For example 3pm, is given by and . The angle made by the shadow of the sun is then given by

[#Ravencroft]

I've taken every algebra, trig and calculus class that can be taken and never had to describe the process of making a sundial.

[SlayerZ99]

I've taken every algebra, trig and calculus class that can be taken and never had to describe the process of making a sundial.

Its for extra credit
My teacher put on a list of a ton of different subjects

This one section is just messing me up so much

[Blockzillahead]

use a watch you homeless

[SlayerZ99]

use a watch you homeless

That goes by standard mean time which I dont want

[Doomonkey]

But in order to find x and y wouldnt I need the radius?


After reading over again I dont think its necessary to have this, I think this is if you want the pointer to touch the ellipse at all times

then again this sections is very confusing for me

You should have this. Also, you don't need x and y. The equation is saying: "Look you don't need R because you divide x and y, but you also don't need x and y because this is also a function of phi and theta."

[SlayerZ99]

You should have this. Also, you don't need x and y. The equation is saying: "Look you don't need R because you divide x and y, but you also don't need x and y because this is also a function of phi and theta."

thank you very much
I still am confused a little but I understand much more now
Just having trouble fully understanding the verification

EDIT: Ok now I fully understand
thanks