help me ...cos and sin value not correct ! whay

[Image Analyst]

What happens if you don't declare them as syms? Just don't declare them at all.

Answer 1

[Steven Lord]

Line 1 is completely unnecessary, since line 2 overwrites those symbolic variables with numeric values.

I'm assuming your trotx and trotz functions call sin and/or cos internally, since there are no actual calls to the trigonometric functions in the code you've shown.

pi is not π. It's close, but your computer doesn't have enough memory to store the exact value of the transcendental number π.

Here are a few potential solutions. I'd probably use sind and cosd.

1) Use sind and cosd (introduced before release R2006a) or sinpi and cospi (introduced in release R2018b) instead of taking the sin or cos of a multiple of 2*pi/360.

>> cos(-90*2*pi/360)
ans =
   6.1232e-17

>> cosd(-90)
ans =
     0
     
>> cospi(-90*2/360)
ans =
     0     

2) Define a1 to be a symbolic variable with the value -90. This would combine and replace lines 1 and 2 assuming you did the same thing for c1, Q2, and d2. In that case, MATLAB will compute a1*2*pi/360 symbolically rather than numerically.

>> a1 = sym(-90);
>> cos(a1*2*pi/360)
ans =
0

[moumene hafidh]

thank you very much