If tanA−tanB=x,cotB−cotA=y..................
(sec(A−B)−1)(sec(A−B)+1)
=sec2(A−B)−1=tan2(A−B)=(tanA−tanB1+tanAtanB)2.....(i)
y=cotB−cotA=tanA−tanBtanAtanB=xtanAtanB
∴tanAtanB=xy.............(ii)
from (i) and (ii), we get
(sec(A−B)−1)(sec(A−B)+1)=(x1+(x/y))2
=x2y2(x+y)2
∴a=b=c=2
∴a+b+c=6