Question

Tan^4x-sec^4x=1-2 sec^2(x)
verify

Answer 1

tan⁴x - sec⁴x = 1 - 2sec²x

tan²x = sec²x - 1

tan⁴x - sec⁴x = 1 - 2sec²x
(tan²x)² - sec⁴x = 1 - 2sec²x
(sec²x - 1)² - sec⁴x = 1 - 2sec²x

(sec²x)² - 2 * sec²x + 1 - sec⁴x = 1 - 2sec²x
sec⁴x - 2 sec²x + 1 - sec⁴x = 1 - 2sec²x

sec⁴x can be cancelled:
- 2 sec²x + 1 = 1 - 2sec²x

1 - 2sec²x = 1 - 2sec²x