sederhanakan (sec x + tan x)(1-sin x)

(1/cos x + sin x /cos x)(1-sin x )
= 1-sin^2 x / cos
= cos^2 x /cos = cos x

sec x = 1/cos x
tan x = sinx/cosx

{(1+sinx)/cosx}(1-sinx)

(1-sin²x) / cosx

cos²x / cosx

cosx