Matlab computing a wrong value

I am trying to do a simple calculation but matlab is outputting a different value than from what it should be, any ideas why?

 R=0.5;
 Cv=0.4;
 B1= 60;

 R= Cv/2*(tan(B1) + tan(B2));
 [B2] = vpasolve([R], [B2]);

 disp(B2);

You are supposed to find that B2 should be around 37.5 but matlab displays a value of -0.3097 so why is matlab getting a different answer?

[Vidhan Malik]

I think it's due to it being in radians but even after you convert it to degrees, the answer comes out to be -17.7 which still isn't correct.

Also when I try to use the code

 R= Cv/2*(tand(B1) + tand(B2));

I get the error of

 Undefined function 'tand' for input
 arguments of type 'sym'.

So why exactly is that error occurring?

First two lines of code are:

 clear,clc;

 syms B1 B2

[John D'Errico]

I answered your problem. It appears that the symbolic toolbox does not use tand. But I show there how to convert between degrees and radians.

[Vidhan Malik]

Sorry didn't receive the notification!

[John D'Errico]

There is a time lag, lol. And half the time, I answer a question, only to find that someone else has already answered while I was writing a wordy dissertation on the problem.

Answer 1

[John D'Errico]

Note that the tan function uses radians, NOT degrees. So you use tan(B1), where B1 is clearly a number written in degrees.

You can either use the function tand, which works in degrees, or you can convert degrees to radians.

Next, first, you set R = 0.5, then you set it equal to Cv/2*(tan(B1)+tan(B2)). This is wrong, since you wish to SOLVE for that.

syms B2
R=0.5;
Cv=0.4;
B1= 60;
B2 = solve(R == Cv/2*(tan(B1*pi/180) + tan(B2*pi/180)))

Note the use of == in there, NOT = as you had done.

B2 =
-(180*atan(3^(½) - 5/2))/pi

vpa(B2)
ans =
37.522431511944199990343681864777

[Vidhan Malik]

Thank you!