Question

найдите sina×cosa если sina+cosa=0.8

Answer 1

$sin(\alpha)+cos(\alpha)=0,8 \mid(^{2})\\ \\ sin^{2}(\alpha)+2*sin(\alpha)*cos(\alpha)+cos^{2}(\alpha)=0,64 \\ \\ 1+2sin(\alpha)*cos(\alpha)=0,64 \\ \\ 2sin(\alpha)*cos(\alpha)=0,64-1 \\ \\ 2sin(\alpha)*cos(\alpha)=-0,36 \\ \\ sin(\alpha)*cos(\alpha)= \frac{-0,36}{2} \\ \\ sin(\alpha)*cos(\alpha)=-0,18$