Vpa Solve solving for B

Hello,

This is a follow up question to this one. Previous Question

For some reason i was previously getting a different answer using vpasolve and vpa which now works and I get the right answers for solving for the Beta variable. I'm now using the code to solve B for when the values of M1=3 and theta2=15. When i do this i start getting results with imaginary answers.

The correct answer should be something like 32.24 but I'm getting:

beta =

84.4217 + 5.8932e-37i

M1 = 3;
P1 = 1;
theta2 = 15;
thetha3 = 20;
gamma = 1.4;

syms beta

tantheta = tand(theta2);

x = 2*cotd(beta)*((M1^2*((sind(beta))^2)-1));
y = M1^2*(gamma+cosd(2*beta))+2;
eqn = x/y;

result = solve(tantheta == eqn, beta);

beta = vpa(result)+180

Answer 1

[Walter Roberson]

M1 = 3;
P1 = 1;
theta2 = 15;
thetha3 = 20;
gamma = 1.4;

syms beta

tantheta = tand(theta2);

x = 2*cotd(beta)*((M1^2*((sind(beta))^2)-1));
y = M1^2*(gamma+cosd(2*beta))+2;
eqn = x/y;

b0 = 1;
result = vpasolve(tantheta == eqn, beta, b0);

beta = vpa(result)+180

beta = 

212.24040018274467042158222540358

[Benneth Perez]

Hello,

Thank you for the help the solution which im looking for is the first one, should be 32.26. 212 does look like a solution however is not the smallest solution(first solution).

Do you mind telling me whath B0 =1; is for ?

My guess is that this is a first guess for the solution computation?

Follow up: Wow! actually this works! Exactly what my code needed, all i needed to do was remove the 180 and it gives me the solution im looking for. Adding 180 gives me the 4 solution.

Thank you