I plotted a RasterBrick, but I want to know the coordinates of each corner. I see that xmin = 3263575, xmax = 3300872, etc., but how are those coordinates?

```
class      : RasterStack 
dimensions : 161, 161, 25921, 12  (nrow, ncol, ncell, nlayers)
resolution : 231.6564, 231.6564  (x, y)
extent     : 3263575, 3300872, -63010.57, -25713.9  (xmin, xmax, ymin, ymax)
crs        : +proj=sinu +lon_0=0 +x_0=0 +y_0=0 +a=6371007.181 +b=6371007.181 +units=m +no_defs 
names      : X2010.01.01, X2010.01.17, X2010.02.02, X2010.02.18, X2010.03.06, X2010.03.22, X2010.04.07, X2010.04.23, X2010.05.09, X2010.05.25, X2010.06.10, X2010.06.26 
min values :        -0.3,        -0.3,        -0.3,        -0.3,        -0.3,        -0.3,        -0.3,        -0.3,        -0.3,        -0.3,        -0.3,        -0.3 
max values :      0.9825,      0.9545,      0.9787,      0.9893,      0.8823,      0.9836,      0.9428,      0.9922,      0.9841,      0.9547,      0.9576,      0.9652 

```