Prove that `cot^-1(13) + cot^-1(21) + cot^-1 (-8) = pi`

cot^-1 (21) + cot^-1(13) + cot^-1 (8) =

Prove that cot^-1 7 + cot^-1 8 + cot^-1 18 = cot^-1 3

Prove that cot(pi/4 - 2 cot^-13) = 7

Prove that cot^-1 7 + cot^-18 + cot^-118 = cot^-1 3 .

Prove that cot^-1x+cot^(-1)(1/x) is a constant.

Solve : cot^-1(2x)+cot^-1(3x)=pi/4

If A = 1/1 cot ^(-1) (1/1) + 1/2 cot^(-1) (1/2) + 1/3 cot ^(-1) ( 1/3) " and " B = 1 cot^(-1) ( 1) + 2 cot^(-1) (2) + 3 cot^(-1) (3) " then " |B - A| " is equal to " (a pi )/b + c/d cot ^(-1) (3) where a,b,c,d in N are in their lowest form , find ( b -a - c - d)

Prove that : tan^-1 x + cot^-1(x+1) = tan^-1(x^2 + x +1)

Prove that : cot 2A= (cot^2 A-1)/(2 cot A) .

Prove that cos(sin^-1(3/5) + cot^-1(3/2)) = 6/(5sqrt13)