Please help to solve this: y=cos^2x - sin^2x
I don't know how to differentiate it. Thanks.
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Assuming that the function is y =cos^2(x)-sin^2(x)
y´= 2cosx(-sinx)- 2sinx(cosx)
thanks for replying. However, the back of the book has a different answer: -2sin2x
could you clarify? Thanks
That´s because sin2x = 2sinxcosx (by double angle trigonometric identity)
-2sin2x = -2(2sinxcosx) = -4sinxcosx, and thats all.
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