Question

Can someone teach me how to verify that this equation is an identity step by step? cosA - sinA = (cos2A)/(cosA + sinA)

Answer 1

that's easy,
use the identity :
cos2A = cos^2 A - sin^2 A

Answer 2

see your right side becomes,
(cos2A)/(cosA + sinA)
= (cos^2 A - sin^2 A)/(cosA + sinA)

Answer 3

then factor out the numerator by using the difference square formula :
a^2 - b^2 = (a+b)(a-b)

Answer 4

ohhhh

Answer 5

i get it, thank you :)

Answer 6

so, it can be
= (cos A - sinA)(cos A + sinA)/(cosA + sinA)
cancel out the similar term ;)

Answer 7

you're welcome