Question

ПОМОГИТЕ!ПОМОГИТЕ!помогите срочно!!прошу​

Answer 1

$sin^2x+cos^2x=1Rightarrowcos x=pmsqrt{1-sin^2x}=pmsqrt{1-frac49}=pmsqrt{frac59}=pmfrac{sqrt5}3\\-fracpi2<x<fracpi2Rightarrowcos x>0\cos x=frac{sqrt5}3\\9sqrt5sin2x=18sqrt5sin xcos x=18sqrt5cdotleft(-frac23right)cdotfrac{sqrt5}9=-2cdot5cdotfrac23=-frac{20}3=-6frac23$