<PRE><B>Question 981304</B>
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T=theta
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cos3T = cos(2T+T)...cos(a+b)=cos(a)cos(b)-sin(a)sin(b) 
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cos3T = cos2TcosT-sin2TsinT...cos(2a)=cos^2(a)-sin^2(a) and sin(2a)=2sinTcosT 
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cos3T = cosT(cos^2T-sin^2T)-sinT(2sinTcosT)
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cos3T = cos^3T-sin^2cosT-2sin^2TcosT
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cos3T = cos^3T-3sin^2TcosT...sin^2(a)=1-cos^2(a)
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cos3T = cos^3T-3(1-cos^2T)(cosT)
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cos3T = cos^3T-3(cosT-cos^3T)
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cos3T = cos^3T+3cos^3T-3cosT
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cos3T = 4cos^3T-3cosT

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