Question

Sa se calucleze sin 4x stiind ca tg x =2

Answer 1

tgx=2 sin/cos=2;sin=cos2=>sin^2x=4cos^2x=>sin^2x=4/5 Sin4x=sin2(2x)=sin(2x)cos(2x)=4sinx cosx *(1-2sin^2x)=4sinx*1/2sinx*(1-4/5)=2sin^2x*1/5=2*4/5*1/5=8/25