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October 9, 2015
Posted by **123university** on Tuesday, January 5, 2010 at 9:22pm.

cos^2x- 2cosx+1

4cos^2x-1

- trig -
**Damon**, Tuesday, January 5, 2010 at 10:28pmcall 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)