buktikan bahwa cos 2x = 2 cos^ x -1

TriGonoMetRi

cos 2x
= cos (x + x)
= cos x cos x - sin x sin x
= cos² x - sin² x
= cos² x - (1 - cos² x)
= 2 cos² x - 1
TerBukTi

cos 2x = cos (x + x)
=cosx cosx - sinx sinx
=cos^2 x-sin^2 x

● sin^2 x=1-cos^2 x

= cos^2 x - (1- cos^2 x)
= 2cos^2x - 1

TERBUKTI