Question

Tan-1 1/3 + tan-1 1/5 + tan-1 1/7 + tan-1 1/8 = pi/4

Answer 1

Answer:

note - tan ^(-1) here means tan inverse

tan ^(-1)(1/3)+tan^(-1)1/7+tan^(-1 )1/8

=tan^(-1)[(1/3+1/7)/(1-1/3×1/7)]+tan^(-1)1/8

=tan^(-1)[{(7+3)/21}/{(21-1)/21}]+tan^(-1)1/8

=tan^(-1)[1/2]+ tan^(-1)1/8

(then the same process

you get)

=tan^(-1)[1]

=pi/4