Blackberry Accelerometer calculations -

i'm playing "accelerometerdemo" in sdk7.0 , have question regarding calculation of "rotation" extracted xyz data.

what want accomplish have virtual "pendulum" points straight down. however, thing gyrating around , not move expect it.

here part of code:

_accchannel.getlastaccelerationdata(_xyz); double roll = mathutilities.atan2(x, z) * 180.0 / math.pi;  graphics.setcolor(color.black); int xcenter = 240; int ycenter = 400;  int length = 220;  int newx1 = (int)(math.cos( roll ) * (double)length) - xcenter; int newy1 = (int)(math.sin( roll ) * (double)length) - ycenter;  graphics.drawline(xcenter, ycenter, newx1, newy1); 

any clues doing wrong?

thanks in advance!

i see @ least 2 problems:

1. math.cos() , math.sin() expect angle inputs in radians, not degrees. using code:

double roll = mathutilities.atan2(x, z) * 180.0 / math.pi; 

you have converted roll degrees.

2. secondly, subtracting center coordinates vector coordinates. believe should adding them, this:

int newx1 = (int)(math.cos( roll ) * (double)length) + xcenter; int newy1 = (int)(math.sin( roll ) * (double)length) + ycenter;