What's the correct answers? quick and concise explanation .

2, 3, 4 and 7  are correc.t

Step-by-step explanation:

sec^2 x = 1 + tan^2x

so sec^2 x - 1 = tan^2 x

So the second choice is correct.

sec^2 x - cos^2x - sin^2x

= sec^2 x - (cos^2x + sin^2 x()

= sec^2 x - 1

The third is correct.

sec^2x / csc^2x =  1 /  cos^2x / 1 / sin^2x

= sin^2x / cos^2x

= tan^2x

= 1 - sec^2 x

So the fourth choice is correct.

1 - cos^2x / cos^2 x

=  sin^2x / soc^2x

= tan^2x

= 1 - sec^2x

The seventh choice is correct.

the answer is a

step-by-step explanation: