sin cos problem. How to solve it

why sind(45)=-0.707

it should be 0.707

and sind(18)=-0.9511

it should be 0.309

what's wrong with it

Answer 1

[Iain]

Theres 2 things that could be wrong.

1. User error - You're actually putting in something like: (-90 + 18) and (-90 + 45), instead of 18 and 45. - This is what I expect

2. A bad prank - Someone has written a function called sind that doesn't do what you think it should, and you're actually using that function.

[tabw]

I guess you are saying that it shifted 90 degree. But, I tried to compensate that by (90+45); still get the negative value.

2. I used the embedded function. I have read the mathwork site. It should be do what I think it should do.

http://www.mathworks.com/help/matlab/ref/sind.html

[Michael Haderlein]

>> sind(45)

ans =

     0.707106781186547

Here, it's doing what it's supposed to do. Please type in

type sind

and post the result here.

[Iain]

If the result of:

 which sind

says built-in, then you're using the built in version. If it says ....\sind.m, then the file can have been altered (which would be a bad prank)

[tabw]

   type sind
  'sind' is a built-in function.

so strange..

After I restart matlab, It functions in a normal way. Thanks all of you