Verify the identity.
1/(tanx-secx) + 1/(tanx+secx) = -2tanx
recall that
(a-b)(a+b) = a^2-b^2
sec^2(x) - 1 = tan^2(x)
put the fractions over a common denominator and watch the answer fall out.
1/(tanx-secx) + 1/(tanx+secx) = -2tanx
(a-b)(a+b) = a^2-b^2
sec^2(x) - 1 = tan^2(x)
put the fractions over a common denominator and watch the answer fall out.