If tan^2x - 3sec^2x + 3 = 0, then the value of x(0 ≤ x ≤ 90°) is :

Using :-

sec²x - tan²x = 1

Given :-

tan²x - 3sec²x + 3 = 0

tan²x - 3 ( 1 + tan²x ) + 3 = 0

tan²x - 3 - 3 tan²x + 3 = 0

- 2 tan²x = 0

tanx = 0

{ we know,    tan 0º = 0 }

So , x = 0º