hey all this one question keeps bugging me if you could help thanks so much!

if it is an identity prove it.

(sinX+cosx)^2=1

if i expand it it becomes

sinx^2+cosx^2+2sinxcosx=1

if i chose to changd sinx^2 to 1-cos^2 it becomes

(1-cosx^2)+cosx^2+sinxcosx=1

so it simplifies to

1+sinxcosx=1

I cant seem to go anywhere from there....if im on the right track please let me know! or is it just not an identity?

THANKS!