#e^(i theta) = cos theta + i sin theta#
#e^(((13pi)/8) i )= cos ((13pi)/8) + i sin ((13pi)/8)#
#~~> 0.3827 - 0.9239 i #, IV Quadrant
#e^(((3pi)/2)i) = cos ((3pi)/2) + i sin ((3pi)/2)#
#=> - i#, III Quadrant.
#e^(((13pi)/8)i) - e^(((3pi)/2)i) = 0.3827 - 0.9239 i - -i #
#color(chocolate)(=> 0.3827 + 0.0761 i #, I Quadrant.