Expert: Ahmed Salami - 9/26/2009

Question
Prove that secA(1-sinA)(secA+tanA) = 1

Answer
Hi Dev,
First, you need remember the identities;
secA = 1/cosA
tanA = sinA/cosA or sinA.secA
sec²A = 1 + tan²A
Now,
secA(1 - sinA)(secA + tanA) = (secA - secA.sinA)(secA + tanA)
                           = (secA - tanA)(secA + tanA)
                           = sec²A - tan²A
                           = 1

Regards