Equations to create this Graph Picture I'm using a online graphing tool "Desmos" to create the image bellow (sunset).

I created the 3 circles to form the sun. Using these equations:

However, I am stuck on creating the images for the other lines.. The curve ones specifically. How should I go about creating the equations for those lines. Any help would be amazing!
 A: You have an equation for the left curve: $f(x)=a+c\log_b(dx)$. This curve has to pass through three points: $(-27,17),(-9,13)$ and $(-3,9)$. That means that for each point $P$ of coordinates $(x_P,y_P)$ you must have $f(x_P)=y_P$. Try to find the coefficients $a,b,c$ and $d$ letting the logarithm pass through the three points.
A: This is how I would attempt this
Ok first for simplicity lets call: 
the line made by joining points $(-17,0)$ and $(-3,9)$ as Line A
and the line made by joining points $(-12,0)$ and $(-3,9)$ as Line B
and the left curve and right curve as shown in the diagram.

Now to find the line of A and B is pretty simple, Il do for one (Line A) to demonstrate it.
The equation of a striaght line is $y=mx+c$
where m is the gradient and c is the intercept.
$m=\frac{y_1-y_2}{x_1-x_2}$
where in Line A the values are :
$x_1=-17$
$x_2=-3$
$y_1=0$
$y_2=9$
Now plugin these and then to now since you know the value of m, to find c
you have 
$y=mx+c$
$c=y-mx$
Put any co ordinate out of the two. Il put $(-3,9)$
and you get 
$c=9-m(-3)$ 
Because you know m you can find c, and this is the equation of line A. Follow the method for line B.

Now for the curves, lets first look at curve on the right side
We know three points on the curve which are $(-27,17)$ , $(-9,3)$ and $(-3,9)$ 
and we know its in the form $y=a+c log_b(dx)$
But there are 4 unkowns you need to solve for a,b,c,d. So that means you need 4 equations. So the first three equations will be subsituting the 3 points that they have given into the equation. Which gives:
$17=a+c log_b(-27d)$
$3=a+c log_b(-9d)$
$9=a+c log_b(-3d)$
And in order to get the 4th equation you should know that, the line A is normal to the point (-3,9) on the curve, this means that you need to differentiate the function $y=a+c log_b(dx)$ and then you get the first derivative which is a function. 
Then to this when you substitute x=-3 to this function ($dy/dx$) you get an expression with a bunch of unknowns. Lets call this expression as T. NOW we want a formula (not an expression) so we should know that the gradient of line A (which you should know by now) multiplied by the T is equal to -1. (This is a rule) 
So there you have it a 4th equation, now you can solve the 4 equations, find the four unknowns and plot this curve.

Now the curve at the Right side , it approximately looks like the mirror image of the curve on the left side at a vertical line (which I will tell in a moment) and they have mentioned a point it meets, so I would say the right hand side is the reflection of the curve on the left side about the line $x=-9$ (the line of reflection). Look closely, or better yet draw the line $x=-9$ and this will become clear to you.
So since you know its the reflection of the left curve (a known curve by now) and you know a point it meets, and you know the line of reflection. I dont think it would be hard to proceed from this point on. Try these, if you get stuck ;) Dont forget to ask.
