Undefined f tand for input arg sym

I receive error "Undefined function 'tand' for input arguments of type 'sym' at line:

v = ...* tand(ea/2));

I tried replacing this 'ea' with any numerical value which resulted in the same error message but for 'cosd':

x = cosd(ea)...

any help would be much appreciated

ea = m + (180/pi20)* ec * sind(m)* (1 + ec *cos(m));

          keeplooping = true;

           while ea > 0.005
              E1 = (ea - (180/pi20)* ec *sind(ea)-m)/(1-ec *cosd(ea));
              E1 = ea;
              keeplooping;
                  if ea <= 0.005
                      keeplooping = false

                      return
                  end
           end

v = 2*atand((sqrt(1+ec))* tand(ea/2));

r = (a *(1-(ec^2))/(1+ec* cosd(v)));

x = cosd(ea) - ec;
y = sind(ea) * sqrt(1 - ec* ec);

r = sqrt(x*x + y*y);
v = atand2(y,x);

Answer 1

[Walter Roberson]

For symbolic inputs, there is no tand(), atand(), atand2(), cosd(), acosd(), sind(), or asind() .

You need to convert the argument to radians yourself, or define sind and so on yourself. For example,

Pi = sym('pi');
sinD = @(x) sin(x*Pi/180);
cosD = @(x) cos(x*Pi/180);
tanD = @(x) tan(x*Pi/180);
atanD = @(x) atan(x) * 180/Pi;
atanD2 = @(y,x) atan2(y, x) * 180/Pi;

ea = m + (180/pi20)* ec * sinD(m)* (1 + ec * cosD(m));    %corrected from original, which had cos(m)

          keeplooping = true;

           while ea > 0.005
              E1 = (ea - (180/pi20)* ec * sinD(ea)-m)/(1 - ec * cosD(ea));
              E1 = ea;
              keeplooping;
                  if ea <= 0.005
                      keeplooping = false

                      return
                  end
           end

v = 2 * atanD((sqrt(1+ec))* tanD(ea/2));

r = (a *(1-(ec^2))/(1+ec* cosD(v)));

x = cosD(ea) - ec;
y = sinD(ea) * sqrt(1 - ec* ec);

r = sqrt(x*x + y*y);
v = atanD2(y,x);

[Cat]

thank you Walter