Question 34343
Prove that 

{{{ tan^2(A) + sec^2(A) = 2sec^2(A) - 1 }}}


This is a straightforward one to prove, since we know that {{{ tan^2(A) + 1 = sec^2(A) }}}.


Using, this as {{{ tan^2(A) = sec^2(A) - 1 }}} we can sub this into the right hand side as:


{{{ tan^2(A) + sec^2(A) }}}
{{{ sec^2(A) - 1 + sec^2(A) }}}
--> {{{ 2sec^2(A) - 1 }}}


jon.