Question

How do you prove `(1-tanx)^2=sec^2x-2tanx`?

Answer 1

Use trig identities: `1 + tan^2 x = 1/cos^2 x = sec^2 x`

`(1 - tan x) = 1 + tan^2 x - 2tan x` = `sec^2 x - 2tan x`