Question

помогите сделать а.б.г

Answer 1

a) $\frac{(1-cosa)(1+cosa)}{sina+sin( \pi -a)}=\frac{1-cos^{2}a}{sina+sina}=\frac{sin^{2}a}{2sina}=0.5*sina$

б) $(5-2 \sqrt{6})^{2}-(3\sqrt{2}-2\sqrt{3})(4\sqrt{2}+8\sqrt{3})=25-20\sqrt{6}+4*6-(12*2+24\sqrt{6}-8\sqrt{6}-16*3)=25-20\sqrt{6}+24-24-24\sqrt{6}+8\sqrt{6}+48=-36\sqrt{6}+73$

г) Если правильно разобрала почерк.

$\left \{ {{a_{5}+a_{10}=-9} \atop {a_{4}+a_{6}=-11}} \right.$

$\left \{ {{a_{1}+4d+a_{1}+9d=-9} \atop {a_{1}+3d+a_{1}+5d=-11}} \right.$

$\left \{ {{2a_{1}+13d=-9} \atop {2a_{1}+8d=-11}} \right.$

$5d=2$
$d=0.4$
$2a_{1}+13d=-9$
$2a_{1}=-9-13d=-9-13*0.4=-14.2$
$S_{10}=\frac{2a_{1}+9d}{2}*10=5*(2a_{1}+9d)=5*(-14.2+9*0.4)=-53$