# trig

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Factor each expression:
cos^2x- 2cosx+1

4cos^2x-1

• trig -

call z = cos x

z^2 -2z +1
(z-1)(z-1)
so
(cosx-1)(cosx+1)

4z^2-1
(2z-1)(2z+1)
(2cosx-1)(2cosx+1)

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