Question

(1+tan alpha)(1-tan alpha)

Answer 1

(a+b) (a-b) = a^2-b^2




Therefore

Ans. 1 -tan^2 alpha

Answer 2

use identity (a+b)(a-b) =a square-b square. so it is =1-tan square alpha= 1-(sec squate alpha-1)= 2-sec square alpha