Need to write a formula in JavaScript

Question

I am aiming to calculate stars' radii. The formula requires three variables, of which I will have two, so I should be able to get the third via basic algebra. Here is the formula:

L = 4 π R^2 s T^4

Where L is the luminosity in Watts, R is the radius in meters, s is the Stefan-Boltzmann constant (5.67 x 10-8 Wm-2K-4), and T is the star's surface temperature in Kelvin.

I will have the luminosity and temperature, and need to derive the radius. Any help writing a function would be greatly appreciated, as I have no experience with maths in JavaScript.

Answer 1

With basic algebra you can deduce that you formula is: R=(L/(4*pi*s*T^4))^0.5

(x^0.5 is the square root of x)

In js, math functions came from the Math package.

To find:

-^x, use Math.pow(base,x);

-the square root, use Math.sqrt(base);

Pi is Math.pi

So basically, your function will look like:

var s = ...;
function R(L, T){
  return Math.sqrt((L/(4*Math.pi*s*Math.pow(T,4))));
}

---

DERIVE???

To derive, it's not requiring really much work, only to calculate the difference between two values divided by the time laps. var x = 0; // x at last data chunk var r = 0; // initial radius

function temperature(X, T, L){ // to find the tangent between the last two point, somewhat similar to derivative
  var R = R(L,T);
  var tangent = (R-r)/(X-x);
  r = R;
  x = X;
  return tangent;
}