How can I write a loop to evaluate theta at every two degrees from 0-360?

n=(360/Dth)+1
theta=0
for I=1:2:n
  R=12  
  w=(2*pi/5)
  Md=50  
  Thetarads= theta*pi/180  
  Id=(.5*Md*R^2)    
  Mp=75  
  Mb=30  
  alpha=0
  u=.8
  L=6*R
  theta=0
  Dth=2
  thetarads=theta*pi/180
  rx=(R)*cos(theta)-L*cos(180)-L
  ry=(R*sin(theta))-(L*sin(180))-(R*sin(theta))
  vx=(-R)*(w)*sin(theta)
  vy=(R)*(w)*cos(theta)
  alpha=0
  ax=(-R)*alpha*sin(theta)-(R*(w^2)*cos(theta))
  ay=(R)*alpha*cos(theta)-(R*w^2*sin(theta))
  theta=theta+Dth
end

[Roger Stafford]

There are a number of errors or questionable items in your code:

1) Inside the for-loop you set theta = 0 so that it will never change.

2) You write sin(theta) and sin(180), and theta and (I suspect) 180 are in degrees, whereas ‘sin’ uses radian measure.

3) In the line

   ry=(R*sin(theta))-(L*sin(180))-(R*sin(theta))

the R*sin(theta) terms cancel each other.

4) You set alpha = 0, so why use it in the lines for ax and ay?

5) Why have you defined Md, Id, Mp, Mb, u. They are never used.

[Emily Gobreski]

thank you so much! I have no idea what I am doing. I really appreciate your time and help! what do i need to do to make sure theta changes?

Answer 1

[Steven Lord]

You probably want simply to use the degree-based trig functions like sind, cosd, etc. instead of sin and cos.

[Emily Gobreski]

thank you! how can i write it in radians and still account for the degree change?

[Chad Greene]

Steven's suggesting an alternative function. If you're working in degrees, you can use sind(theta) or you can use sin(theta*pi/180). They will both give the same result.