trigonemtric identity question

Question

how does sinx+cosx when squared equal to sin^2x + 2sinxcosx + cos^2x ?

Answer 1

Urauf,

 

There are 3 basic factoring patterns you need to know - for math, for the SAT, for the ACT - and they are:

 

(x+y)^2 = x^2 + xy + xy + y^2 = x^2 + 2xy + y^2

 

(x-y)^2 = x^2 - xy - xy + y^2 = x^2 - 2xy + y^2

 

(x+y)(x-y) = x^2 + xy - xy - y^2 = x^2 - y^2

 

You must know these!

 

So, if x in the above equation is (sin(x)) and y is (cos(x)), well, you see the pattern.