If $cosx=2/5$ , how do you find $sin2x$ ?

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Answer 1 · 2016-07-30T22:34:45

$sin 2x=2/5 sqrt(3/5)$

$cos x=2/5" ; "sin 2x=?$

$sin2x=sin x*cos x+cos x*sin x$

$sin 2x=2*sin x*cos x$

$"so ;" sin x=sqrt(1-cos^2 x)$

$"we can write as ;"$

$sin 2x=sqrt (1-cos^2 x)*cos x$

$sin 2x=sqrt(1-2/5)*2/5$

$sin 2x=sqrt((5-2)/5)*2/5$

$sin 2x=sqrt(3/5)*2/5$

$sin 2x=2/5 sqrt(3/5)$

If cosx=2/5cosx=2/5, how do you find sin2xsin2x?