Q.

Exhaustive value of x such that cos-1(8x1+16x2)=-π2+2tan-1(4x)

1 (18,∞)  
2 (116,18)  
3 [14,∞)  
4 (18,14)  

Ans.

(3)

On solving π2-sin-1(2×4x1+(4x)2)=-π2+2tan-1(4x)

⇒2tan-1(4x)=π-sin-1(2(4x)1+(4x)2)

4x≥1; x≥14