Answer:
resultant increases by factor of 1.12
Step-by-step explanation:
EDITED :
Assume force = 1 for simplicity and one vector is on the x axis 
at 55 degrees 
 horizontal components = 1 + cos 55 = 1.574
 vertical component = sin 55 = .8192 
 resultant = 1.77
at 15 degrees 
 horizontal components = 1 + cos 15 = 1.966
 vertical component = sin 15 = .2588
 resultant = 1.98 
resultant increases by 1.98 / 1.77 = 1.12 original