since you are trying to find the direction you have to use
tan theta= y/x
tan theta= 26/-5
theta= tan^-1I26/-5I
theta= 79.11 degrees but since (-5,26) is found in the second quadrant you have to substract 180 - a to obtain the direction angle
theta= 180 -a
=180 - 79.11
theta = 100.88 degrees
vector v has a direction angle of 100.88 degrees
