I would like to compute the expression displayed in the image with the Raster Calculator tool by using the slope (degrees) derived from the SRTM 30m DEM data. However, it results in NoData values for some of the pixels. The problematic part of the formula that is responsible for the NoData values it seems to be the part surrounded by the red box. This is happening to pixels that have negative sinθ values. In particular, when I solely calculate the sin of the slope raster the output is correct and contains both positive and negative values. However, when I use the power of 0.8 the negatives sinθ values lead to NoData values.
P.S. None of my DEM and thus slope pixels have NoData values. I also try to convert my slope raster to unsigned bit and then try the calculations again (without using the Float() function), but still the NoData values were there. The Power() function does not work as well.