Why the function like (1 - cosd(x)) / cosd(x) doesn't create an vector and can't plot?

I want to plot an function for relative deviation but I got the problem to create the vector. I cant plotting anything.

I try to have on the x-axis the angle in GRAD and on the y-axis the relativ deviation in %.

Do you know where there problem is? I got the following code:

x=-25:0.1:25;

%Grad in Bogenmaß
R = deg2rad(x); 

%sin und cos in degree sind sind() und cosd()
F_rel_a = (R - sind(x))/sind(x);
F_rel_c = (1 - cosd(x))/cosd(x);

%%% y = F_rel_a * 100; %not in use

%plotting
figure
plot(x, F_rel_a)
hold on 
plot(F_rel_c)
hold off

%%% axis([-25 25 0 2]) %not in use
xlabel('Pendelwinkel in Grad [°]');
ylabel('Relative Abweichung in [%]');
legend({'$sin(\varphi) \approx \varphi$', '$cos(\varphi) \approx 1$'},'Interpreter','latex')

[Stephen23]

"Do you know where there problem is?"

Not using the correct operator: https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html

Answer 1

[Bruno Luong]

Change / to ./, the "/" is matrix left-division and does something you won't expect for vectors

x=-25:0.1:25;
%Grad in Bogenmaß
R = deg2rad(x); 
%sin und cos in degree sind sind() und cosd()
F_rel_a = (R - sind(x))./sind(x);
F_rel_c = (1 - cosd(x))./cosd(x);
%%% y = F_rel_a / 100; %not in use
%plotting
figure
plot(x, F_rel_a)
hold on 
plot(F_rel_c)
hold off
%%% axis([-25 25 0 2]) %not in use
xlabel('Pendelwinkel in Grad [°]');
ylabel('Relative Abweichung in [%]');
legend({'$sin(\varphi) \approx \varphi$', '$cos(\varphi) \approx 1$'},'Interpreter','latex')

[Janis Anger]

Ah perfectly, it works! Thank you! I also see I forgot the x in one of the plots:

hold on 
plot(x, F_rel_c) %<----- insert x
hold off

Answer 2

[Torsten]

%sin und cos in degree sind sind() und cosd()
F_rel_a = (R - sind(x))./sind(x)
F_rel_c = (1 - cosd(x))./cosd(x)

instead of

%sin und cos in degree sind sind() und cosd()
F_rel_a = (R - sind(x))/sind(x)
F_rel_c = (1 - cosd(x))/cosd(x)

[Janis Anger]

Yes great! It works, thank you too for the fast response.