solving Diffrential equation one parameter related to another one

Hello every body

I am trying to solve a diffrential equation but in a two days I cannot solve it. My parameters related to each other which method should I use to get answer my answer should be a matrix with 360 numbers?

%% Input Parameters

Rs = 200;

Rr = 180;

Phi = 180;

t = 0:1:360;

e = Rs - Rr;

%% Calculation

B = [e*cosd(Phi-t)]+[(Rs)^2-(e^2)*(sind(Phi-t).^2)].^0.5;

dx/dt = (B^2)-(Rr^2)

Answer 1

[Alan Stevens]

Like this?

%% Input Parameters
Rs  = 200;
Rr  = 180;
Phi = 180;
t = 0:1:359;
e   = Rs - Rr;
%% Calculation
B = @(t) e*cosd(Phi-t)+(Rs^2-e^2*sind(Phi-t).^2).^0.5; 
dxdt = @(t,x) B(t)^2 - Rr^2;

x0 = 0; %%%% needs an initial value for x
[~,x] = ode45(dxdt, t, x0);

plot(t,x),grid
xlabel('t'),ylabel('x')