Difficulty finding an identy for the sinxcosx
asked May 19, 2013 in Trigonometry Answers by anonymous

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sin(x)(sin(x)+cos(x)). If this expression equals zero, sin(x)=0 or sin(x)=-cos(x), so tan(x)=-1.

Solutions: sin(x)=0: x=n(pi); tan(x)=-1: x=(4n-1)(pi)/4 where n is an integer. x is in radians. To convert to degrees put (pi)=180: 0, 180, 360, ..., 135, 315, ... for example.

cos(2x)=1-2sin^2(x), so sin^2(x)=(1-cos(2x))/2

sin(2x)=2sin(x)cos(x), so sin(x)cos(x)=(1/2)sin(2x)

sin^2(x)+sin(x)cos(x)=(1/2)(1-cos(2x)+sin(2x)). Above solutions apply.

answered Nov 21, 2015 by Rod Top Rated User (570,580 points)

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