The value of tan-1(1) + cos-1(-1/2) + sin-1(-1/2) is equal to-

Let  tan^-1 (1) = x. Then, tan x =1 = tan (π/4) 

so cos^-1 (1) = (π/4)

Let, cos^-1(-1/2) = y. Then cos y = -1/2= cos(π/3) = cos(π-π/3)= cos(π/3)

so cos^-1 (-1/2) = (2π/3)

Let, sin^-1(-1/2) = z. Then sin z = -1/2= -sin(π/6) = sin(-π/6)

so sin^-1 (-1/2) = (π/6)

so, tan^-1(1) + sin^-1(-1/2)+ cos^-1(-1/2)  

= π/4+ π/2 = 3π/4