Q.

Let a≤tan-1x+cot-1x+sin-1x≤b. If α and β denote the minimum and maximum possible values of a and b respectively, then: 

1 α=0, β=π  
2 α=0, β=π2  
3 α=π2, β=π  
4 α=-π2, β=π2  

Ans.

(1)

Ans.   α=0, β=π

Explanation:

We know that

   tan-1x+cot-1x=π2

tan-1x+cot-1x+sin-1x=π2+sin-1x

                  -π2≤sin-1x≤π2

⇒-π2+π2≤sin-1x+π2≤π2+π2

⇒0≤π2+sin-1x≤π

⇒0≤tan-1x+cot-1x+sin-1x≤π

∴   α=0,    β=π