Improve software responsiveness when slider is manipulated in windows phone - windows-phone

Question

I have a slider in my windows phone 7.1 project. When manipulated, this slider fires an event which starts a background worker to performs several trigonometric operations.
If I move the cursor on the slider, I have a certain delay in the response although I have implement background worker cancelAsync method in manipulationstarted event, I would like more responsiveness, how can I achieve this?
Code:
private void sliderCosinus_ManipulationStarted(object sender,ManipulationStartedEventArgs e)
{
if (bw.WorkerSupportsCancellation == true)
{
bw.CancelAsync(); // Cancel the asynchronous operation.
}
}
private void sldCosinus_ManipulationCompleted(object sender, ManipulationCompletedEventArgs e)
{
try
{
Value = Convert.ToInt32(sldCosinus.Value) * 10;
}
catch
{
// errore message here
}
finally
{
}
}
private void bw_DoWork(object sender, DoWorkEventArgs e)
{
BackgroundWorker worker = sender as BackgroundWorker;
if ((worker.CancellationPending == true))
{
e.Cancel = true;
}
else
{
Dispatcher.BeginInvoke(() => app.IsEffectApplied=TrigonometricTrans()
// TrigonomtriecTrans calculate sin and cosinus for every pixel in image
}
}
private void bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
// progress bar here
}
private void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if ((e.Cancelled == true))
{
//this.tbProgress.Text = "Canceled!";
}
else if (!(e.Error == null))
{
//this.tbProgress.Text = ("Error: " + e.Error.Message);
}
else
{
DoubleBufferToScreen();
}
}