Simplify
(sinA +cosA) (sinA-cosA)

-cos(2A)

Step-by-step explanation:

We know that (a+b) (a-b) = a^2-b^2

So it means we can simplify to sin^2(A)-cos^2(A) and we know cos^2(A) - sin^2(A) = cos(2A) but we will just multiply by -1 and we get - cos(2A)

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make sure you have version 2.50

try looking in the very back of the book : )

step-by-step explanation:

you can download it here