How do you prove (sec x + tan x)(1 - sin x) = cos x ?

1 Answer
Feb 21, 2017

See explanation...

Explanation:

Use:

sec x = 1/cos x

tan x = sin x/cos x

cos^2 x + sin^2 x = 1

Then:

(sec x + tan x)(1 - sin x) = (1/cos x + sin x/cos x)(1- sin x)

color(white)((sec x + tan x)(1 - sin x)) = ((1+sin x)(1- sin x))/cos x

color(white)((sec x + tan x)(1 - sin x)) = (1-sin^2 x)/cos x

color(white)((sec x + tan x)(1 - sin x)) = cos^2 x/cos x

color(white)((sec x + tan x)(1 - sin x)) = cos x