How do you simplify sec^2x-tan^2x

i need to know how to simplify this answer...please help me:)

sec²(x) - tan²(x) is equal to 1. That's a standard identity that would probably be good to memorize.

Here's a derivation using the identity sin²(x) + cos²(x) = 1:
sec²(x) - tan²(x)
1/cos²(x) - sin²(x)/cos²(x), since sec(x) = 1/cos(x) and tan(x) = sin(x)/cos(x)
[1 - sin²(x)] / cos²(x)
[1 - sin²(x)] / [1 - sin²(x)], since sin²(x) + cos²(x) = 1, i.e., cos²(x) = 1 - sin²(x)
1

Hope that helps :)

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

sec^2x - tan^2x
= 1/cos^2x - sin^2x/cos^2x
= (1 - sin^2x)/cos^2x
= cos^2x/cos^2x
= 1