If tan^4x - tan^2x= 1, then the value of sin^4x + sin^2x is :

$tan^4x - tan^2x= 1$

tan4 x = 1 + tan²x

tan4 x = sec²x      ( sec²x  - tan²x = 1 )

sin4 x = cos²x

Now,

$sin^4x + sin^2x$

= cos²x  + sin²x 

= 1        ( cos²x  + sin²x  = 1 )