I'm not sure what is wrong with this code regarding the sin and cos function.

Hello, I have a problem with the following code:

angle=input('what is the angle in degrees: ');

t=angle*(pi/180);

if cos(t)<10^(-20)
    disp('error! cos is close to zero');
else
    y=sin(t)/cos(t);
    fprintf('tan is equal to %f',y);
end

My professor said that sin and cos work in radians so I converted the degrees to radians. However, whenever I test for something like 90 degrees (when cos is 0), it should be displaying the error message, but it's not.

I get the following

what is the angle in degrees: 90
tan is equal to 16331239353195370.000000>>

Answer 1

[Youssef Khmou]

Like Azzi said, pi contains infinite decimal numbers, To avoid this ambiguity i recommend you to use the degree functions instead of radians cosd and sind,

 cosd(90)=0
 cos(pi/2)=6.1232e-017

[liv]

This fixed it. Thank you so much.

[Youssef Khmou]

if the problem is solved, accept the answer.

Answer 2

[Azzi Abdelmalek]

You can check the value of cos(90*pi/180) and compare it with 10^(-20)

[liv]

I just tried that and it says the value is false.

cos(90*pi/180)<10^-20

ans =

       0

>> cos(pi/2)

ans =

     6.1232e-17

but cos(pi/2) is zero. Would you know why MatLab is not displaying it as zero?=/ And thank you for your earlier response; it helped me see where the problem is.

[Azzi Abdelmalek]

Type

pi

is it an exact pi?

[liv]

it gives

pi

ans =

      3.1416

[Azzi Abdelmalek]

OK, you know that the exact pi contains much more decimals. what Matlab or any other langage di is an approximation of pi

[liv]

Thank you very much!