Question

A+B= 45 to cota-1. cot b-1=2

Answer 1

cot(a + b) =cot b .cot a -1 / cot a + cot b
we know that cot 45 =1
it is given that a + b = 45
cot (a +b) =cot 45
so, 1 = cot b . cot a -1 / cot a + cot b
     cot a + cot b = cot b .cot a -1
    cot b . cot a -cot a - cot b = 1
adding both side 1
then we get (cot a - 1) (cot b - 1) =2
Hence proved