Mathematics
meli3
2016-04-16 00:59:51
Verify the identity. Show work please
ANSWERS
hoops33day
2016-04-16 07:03:05

cos(3x) = cos( x +2x) = cos(x)*cos(2x) - sin(x)*sin(2x) = cos(x)*(cos^2(x) - sin^2(x)) - sin(x) * 2 * sin(x)*cos(x) = cos^3(x) - sin^2(x)*cos(x) - 2*sin^2(x)*cos(x) = cos^3(x) - 3*sin^2(x)*cos(x) = cos(x)*( cos^2(x) - 3*sin^2(x) )= cos(x)*( 1 - sin^2(x) - 3*sin^2(x)) = cos(x)*(1-4*sin^2(x)), so that cos^3(x)/cos(x)= 1-4*sin^2(x) That was fun!

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