Question

Which expression is equivalent to sec^2x − 1?

cot2x
tan2x
csc2x
cos2x

Answer 1

sec(x)=1/cos(x) so sec^2x=1/cos^2x

now take the identity:
sin^2x+cos^2x=1

divide all terms by cos^2x to get
sin^2x/cos^2x+1=1/cos^2x

then simplify using sin/cos = tan and 1/cos = sec

tan^2x+1=sec^2x

then just subtract 1 from each side

sec^2x-1=tan^2x

Answer 2

so b ?

Answer 3

if b is \[\tan ^2(x) \] then yes